Phosphorescent organometallic iridium complex, light-emitting element, light-emitting device, electronic device, and lighting device

ABSTRACT

As a novel substance having a novel skeleton, provided is a novel phosphorescent organometallic iridium complex that can emit phosphorescence in a blue green to red wavelength region and has high emission efficiency. The phosphorescent organometallic iridium complex has a ligand having a pyridyl pyrimidine skeleton, i.e., the phosphorescent organometallic iridium complex has a ligand having a structure represented by the following general formula (G0). 
                         
Note that in the formula, R 1  and R 4  to R 6  separately represent hydrogen or an alkyl group having 1 to 6 carbon atoms; and R 2  and R 3  separately represent any of hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenyl group that may have a substituent, and a pyridyl group that may have a substituent.

BACKGROUND OF THE INVENTION

1. Field of the Invention

One embodiment of the present invention relates to a phosphorescentorganometallic iridium complex that is capable of converting a tripletexcited state into luminescence. In addition, one embodiment of thepresent invention relates to a light-emitting element, a light-emittingdevice, an electronic device, and a lighting device each including thephosphorescent organometallic iridium complex.

2. Description of the Related Art

A light-emitting element having a structure in which a light-emittinglayer containing an organic compound that is a light-emitting substanceis provided between a pair of electrodes has attracted attention as anext-generation flat panel display element in terms of characteristicssuch as being thin and light in weight, high speed response, and directcurrent low voltage driving. Further, a display including thislight-emitting element is superior in contrast, image quality, and wideviewing angle.

Some of organic compounds which can be used for a light-emitting layerare capable of emitting phosphorescence from an excited state.Phosphorescence refers to luminescence generated by transition betweenenergies of different multiplicity. In an ordinary organic compound,phosphorescence refers to luminescence that is generated at the time ofrelax from a triplet excited state to a singlet ground state (incontrast, fluorescence refers to luminescence that is generated at thetime of relax from a singlet excited state to a singlet ground state).When such a compound capable of emitting phosphorescence, i.e.,converting a triplet excited state into luminescence (hereinafterreferred to as phosphorescent compound), is used as a light-emittingsubstance in a light-emitting layer, internal quantum efficiency can beincreased; thus, a highly efficient light-emitting element can beobtained.

A phosphorescent organometallic iridium complex that contains iridium orthe like as a central metal is particularly attracting attention as aphosphorescent compound because of its high phosphorescence quantumyield (refer to Patent Document 1, Patent Document 2, and PatentDocument 3, for example).

REFERENCE Patent Document

-   [Patent Document 1] Japanese Published Patent Application No.    2007-137872-   [Patent Document 2] Japanese Published Patent Application No.    2008-069221-   [Patent Document 3] International Publication WO 2008/035664    Pamphlet

SUMMARY OF THE INVENTION

While blue or green phosphorescent materials have been developed asreported in Patent Documents 1 to 3, what is also important in view ofextension of the range of light-emitting materials is development ofmaterials having novel skeletons.

Thus, as a novel substance having a novel skeleton, one embodiment ofthe present invention provides a novel phosphorescent organometalliciridium complex that can emit phosphorescence in a blue green to redwavelength region and has high emission efficiency. Further, an objectof one embodiment of the present invention is to provide alight-emitting element, a light-emitting device, an electronic device,or a lighting device each having high emission efficiency.

One embodiment of the present invention is a phosphorescentorganometallic iridium complex with a ligand having a pyridyl pyrimidineskeleton. A phosphorescent organometallic iridium complex with a ligandhaving a pyrimidine skeleton having a pyridyl group at the 4-position ispreferable, and a phosphorescent organometallic iridium complex with aligand having a 4-(3-pyridyl)pyrimidine skeleton or a4-(4-pyridyl)pyrimidine skeleton is more preferable. Further, astructure of one embodiment of the present invention is a phosphorescentorganometallic iridium complex with a ligand having a structurerepresented by the following general formula (G0).

Note that in the formula, R¹ and R⁴ to R⁶ separately represent hydrogenor an alkyl group having 1 to 6 carbon atoms; and R² and R³ separatelyrepresent any of hydrogen, an alkyl group having 1 to 6 carbon atoms, aphenyl group that may have a substituent, and a pyridyl group that mayhave a substituent.

Another embodiment of the present invention is a phosphorescentorganometallic iridium complex having a structure represented by thefollowing general formula (G0′).

Note that in the formula, R¹ and R⁴ to R⁶ separately represent hydrogenor an alkyl group having 1 to 6 carbon atoms; and R² and R³ separatelyrepresent any of hydrogen, an alkyl group having 1 to 6 carbon atoms, aphenyl group that may have a substituent, and a pyridyl group that mayhave a substituent.

In particular, a phosphorescent organometallic iridium complex havingthe structure which is represented by the general formula (G0′) and inwhich the lowest triplet excited state is formed is preferable becausephosphorescence can be efficiently emitted. To achieve such a mode,another skeleton (another ligand) which is included in thephosphorescent organometallic iridium complex may be selected such thatthe lowest triplet excitation energy of the structure is equal to orlower than the lowest triplet excitation energy of the another skeleton(the another ligand), for example. With such a structure, regardless ofwhat a skeleton (ligand) other than the structure is, the lowest tripletexcited state is formed by the structure at last, so thatphosphorescence originating from the structure is obtained. Therefore,phosphorescence can be highly efficiently obtained. A typical example isvinyl polymer having the structure as a side chain.

Further, another embodiment of the present invention is a phosphorescentorganometallic iridium complex having a structure represented by thefollowing general formula (G1).

Note that in the formula, R¹ and R⁴ to R⁶ separately represent hydrogenor an alkyl group having 1 to 6 carbon atoms; and R² and R³ separatelyrepresent any of hydrogen, an alkyl group having 1 to 6 carbon atoms, aphenyl group that may have a substituent, and a pyridyl group that mayhave a substituent.

Further, another embodiment of the present invention is a phosphorescentorganometallic iridium complex having a structure represented by thefollowing general formula (G2).

Note that in the formula, R¹ and R⁴ to R⁶ separately represent hydrogenor an alkyl group having 1 to 6 carbon atoms; and R² and R³ separatelyrepresent any of hydrogen, an alkyl group having 1 to 6 carbon atoms, aphenyl group that may have a substituent, and a pyridyl group that mayhave a substituent. Further, L represents a monoanionic ligand.

Further, another embodiment of the present invention is a phosphorescentorganometallic iridium complex having a structure represented by thefollowing general formula (G3).

Note that in the formula, R¹ and R⁴ to R⁶ separately represent hydrogenor an alkyl group having 1 to 6 carbon atoms; and R² and R³ separatelyrepresent any of hydrogen, an alkyl group having 1 to 6 carbon atoms, aphenyl group that may have a substituent, and a pyridyl group that mayhave a substituent. Further, R¹¹ to R¹³ separately represent hydrogen oran alkyl group having 1 to 6 carbon atoms.

Further, another embodiment of the present invention is a phosphorescentorganometallic iridium complex represented by the following structuralformula (100).

Further, another embodiment of the present invention is a phosphorescentorganometallic iridium complex represented by the following structuralformula (101).

Further, another embodiment of the present invention is a phosphorescentorganometallic iridium complex represented by the following structuralformula (102).

In the above-described phosphorescent organometallic iridium complexesaccording to embodiments of the present invention, a structure with aligand having a pyridyl pyrimidine skeleton increases both molarabsorption coefficient and quantum yield which determine the intensityof phosphorescence. Further, the structure with a ligand having apyridyl pyrimidine skeleton increases the LUMO level in the negativedirection. That is, electrons can be injected efficiently; accordingly,by using the phosphorescent organometallic iridium complex together witha material by which holes can be injected efficiently in a similarmanner, the recombination probability of electrons and holes increases,and a light-emitting element with high emission efficiency can beobtained.

Further, by using the phosphorescent organometallic iridium complexaccording to one embodiment of the present invention for alight-emitting element, a highly efficient element can be fabricated.Thus, one embodiment of the present invention also includes alight-emitting element including the phosphorescent organometalliciridium complex according to one embodiment of the present invention.

Furthermore, one embodiment of the present invention includes not only alight-emitting device including the light-emitting element but also anelectronic device and a lighting device each including thelight-emitting device. Accordingly, a light-emitting device in thisspecification refers to an image display device or a light source(including a lighting device). The light-emitting device also includesthe following modules in its category: a module in which a connectorsuch as a flexible printed circuit (FPC), a tape automated bonding (TAB)tape, or a tape carrier package (TCP) is attached to a light-emittingdevice; a module having a TAB tape or a TCP provided with a printedwiring board at the end thereof; and a module having an integratedcircuit (IC) directly mounted over a light-emitting device by a chip onglass (COG) method.

One embodiment of the present invention can provide a novelphosphorescent organometallic iridium complex. According to oneembodiment of the present invention, a phosphorescent organometalliciridium complex which keeps high quantum efficiency and emitsphosphorescence in the blue green to red wavelength region can beobtained. In addition, according to one embodiment of the presentinvention, a light-emitting element, a light-emitting device, anelectronic device, or a lighting device each including such aphosphorescent organometallic iridium complex and having high emissionefficiency can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 illustrates a structure of a light-emitting element;

FIG. 2 illustrates a structure of a light-emitting element;

FIGS. 3A and 3B illustrate structures of light-emitting elements;

FIG. 4 illustrates a light-emitting device;

FIGS. 5A and 5B illustrate a light-emitting device;

FIGS. 6A to 6D illustrate electronic devices;

FIGS. 7A to 7C illustrate an electronic device;

FIG. 8 illustrates lighting devices;

FIG. 9 shows a ¹H-NMR chart of a phosphorescent organometallic iridiumcomplex represented by a structural formula (100);

FIG. 10 shows an ultraviolet-visible absorption spectrum and an emissionspectrum of the phosphorescent organometallic iridium complexrepresented by the structural formula (100);

FIG. 11 shows a ¹H-NMR chart of a phosphorescent organometallic iridiumcomplex represented by a structural formula (102);

FIG. 12 shows an ultraviolet-visible absorption spectrum and an emissionspectrum of the phosphorescent organometallic iridium complexrepresented by the structural formula (102);

FIG. 13 shows a ¹H-NMR chart of a phosphorescent organometallic iridiumcomplex represented by a structural formula (101);

FIG. 14 shows an ultraviolet-visible absorption spectrum and an emissionspectrum of the phosphorescent organometallic iridium complexrepresented by the structural formula (101);

FIG. 15 illustrates a light-emitting element;

FIG. 16 shows voltage-luminance characteristics of a light-emittingelement 1 and a comparative light-emitting element 1;

FIG. 17 shows luminance-current efficiency characteristics of thelight-emitting element 1 and the comparative light-emitting element 1;

FIG. 18 shows luminance-external quantum efficiency characteristics ofthe light-emitting element 1 and the comparative light-emitting element1;

FIG. 19 shows emission spectra of the light-emitting element 1 and thecomparative light-emitting element 1;

FIG. 20 shows voltage-luminance characteristics of a light-emittingelement 2 and a comparative light-emitting element 2;

FIG. 21 shows luminance-current efficiency characteristics of thelight-emitting element 2 and the comparative light-emitting element 2;

FIG. 22 shows luminance-external quantum efficiency characteristics ofthe light-emitting element 2 and the comparative light-emitting element2;

FIG. 23 shows emission spectra of the light-emitting element 2 and thecomparative light-emitting element 2;

FIG. 24 shows LC/MS measurement results of the phosphorescentorganometallic iridium complex represented by the structural formula(100);

FIG. 25 shows LC/MS measurement results of the phosphorescentorganometallic iridium complex represented by the structural formula(102);

FIG. 26 shows LC/MS measurement results of the phosphorescentorganometallic iridium complex represented by the structural formula(101);

FIG. 27 shows a ¹H-NMR chart of a phosphorescent organometallic iridiumcomplex represented by a structural formula (117); and

FIG. 28 shows an ultraviolet-visible absorption spectrum and an emissionspectrum of the phosphorescent organometallic iridium complexrepresented by the structural formula (117).

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the drawings. Note that the present invention is notlimited to the following description, and various changes andmodifications can be made without departing from the spirit and scope ofthe invention. Therefore, the present invention should not be construedas being limited to the description in the following embodiments.

Embodiment 1

In this embodiment, phosphorescent organometallic iridium complexesaccording to embodiments of the present invention are described.

One embodiment of the present invention is a phosphorescentorganometallic iridium complex with a ligand having a pyridyl pyrimidineskeleton. As a specific example of the ligand, a ligand having apyrimidine skeleton having a pyridyl group at the 4-position can begiven, and more specifically, a ligand having a 4-(3-pyridyl)pyrimidineskeleton or a 4-(4-pyridyl)pyrimidine skeleton can be given.

Further, one embodiment of the present invention is a phosphorescentorganometallic iridium complex with a ligand having a structurerepresented by the following general formula (G0).

In the general formula (G0), R¹ and R⁴ to R⁶ separately representhydrogen or an alkyl group having 1 to 6 carbon atoms; and R² and R³separately represent any of hydrogen, an alkyl group having 1 to 6carbon atoms, a phenyl group that may have a substituent, and a pyridylgroup that may have a substituent.

Another embodiment of the present invention is a phosphorescentorganometallic iridium complex having a structure represented by thefollowing general formula (G0′).

In the general formula (G0′), R¹ and R⁴ to R⁶ separately representhydrogen or an alkyl group having 1 to 6 carbon atoms; and R² and R³separately represent any of hydrogen, an alkyl group having 1 to 6carbon atoms, a phenyl group that may have a substituent, and a pyridylgroup that may have a substituent.

In particular, a phosphorescent organometallic iridium complex havingthe structure which is represented by the general formula (G0′) and inwhich the lowest triplet excited state is formed is preferable becausephosphorescence can be efficiently emitted. To achieve such a mode,another skeleton (another ligand) which is included in thephosphorescent organometallic iridium complex may be selected such thatthe lowest triplet excitation energy of the structure is equal to orlower than the lowest triplet excitation energy of the another skeleton(the another ligand), for example. With such a structure, regardless ofwhat a skeleton (ligand) other than the structure is, the lowest tripletexcited state is formed by the structure at last, so thatphosphorescence originating from the structure is obtained. Therefore,phosphorescence can be highly efficiently obtained. A typical example isvinyl polymer having the structure as a side chain.

Another embodiment of the present invention is a phosphorescentorganometallic iridium complex having a structure represented by thefollowing general formula (G1).

In the general formula (G1), R¹ and R⁴ to R⁶ separately representhydrogen or an alkyl group having 1 to 6 carbon atoms; and R² and R³separately represent any of hydrogen, an alkyl group having 1 to 6carbon atoms, a phenyl group that may have a substituent, and a pyridylgroup that may have a substituent.

Another embodiment of the present invention is a phosphorescentorganometallic iridium complex having a structure represented by thefollowing general formula (G2).

In the general formula (G2), R¹ and R⁴ to R⁶ separately representhydrogen or an alkyl group having 1 to 6 carbon atoms; and R² and R³separately represent any of hydrogen, an alkyl group having 1 to 6carbon atoms, a phenyl group that may have a substituent, and a pyridylgroup that may have a substituent. Further, L represents a monoanionicligand.

Here, it is preferable that L that is the monoanionic ligand be any ofthe following specific examples: a monoanionic bidentate chelate ligandhaving a beta-diketone structure, a monoanionic bidentate chelate ligandhaving a carboxyl group, a monoanionic bidentate chelate ligand having aphenolic hydroxyl group, and a monoanionic bidentate chelate ligand inwhich two ligand elements are both nitrogen. A monoanionic bidentatechelate ligand having a beta-diketone structure is particularlypreferable. A beta-diketone structure is preferably included because asolubility of a phosphorescent organometallic iridium complex in anorganic solvent becomes higher and purification becomes easier. Further,a beta-diketone structure is preferably included because aphosphorescent organometallic iridium complex with high emissionefficiency can be obtained. Furthermore, inclusion of a beta-diketonestructure has advantages such as a higher sublimation property andexcellent evaporativity.

Specifically, L that is the monoanionic ligand is preferably a ligandrepresented by any of the following general formulae (L1) to (L6).

In the general formulae (L1) to (L6), R¹¹ to R⁴² separately representany of hydrogen, a substituted or unsubstituted alkyl group having 1 to4 carbon atoms, a halogen group, a vinyl group, a substituted orunsubstituted haloalkyl group having 1 to 4 carbon atoms, a substitutedor unsubstituted alkoxy group having 1 to 4 carbon atoms, and asubstituted or unsubstituted alkylthio group having 1 to 4 carbon atoms.Further, A¹ to A³ separately represent any of nitrogen, sp² hybridizedcarbon bonded to hydrogen, and sp² hybridized carbon bonded to any of analkyl group having 1 to 4 carbon atoms, a halogen group, a haloalkylgroup having 1 to 4 carbon atoms, and a phenyl group.

Another embodiment of the present invention is a phosphorescentorganometallic iridium complex having a structure represented by thefollowing general formula (G3).

In the general formula (G3), R¹ and R⁴ to R⁶ separately representhydrogen or an alkyl group having 1 to 6 carbon atoms; and R² and R³separately represent any of hydrogen, an alkyl group having 1 to 6carbon atoms, a phenyl group that may have a substituent, and a pyridylgroup that may have a substituent. Further, R¹¹ to R¹³ separatelyrepresent hydrogen or an alkyl group having 1 to 6 carbon atoms.

Note that specific examples of the alkyl group having 1 to 6 carbonatoms in R¹ to R⁶ in the general formulas (G0), (G0′), (G1), (G2), and(G3) and in R¹¹ to R¹³ in the general formula (G3) include a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, a sec-butyl group, an isobutyl group, a tert-butyl group, apentyl group, an isopentyl group, a sec-pentyl group, a tert-pentylgroup, a neopentyl group, a hexyl group, an isohexyl group, a sec-hexylgroup, a tert-hexyl group, a neohexyl group, a 3-methylpentyl group, a2-methylpentyl group, a 2-ethylbutyl group, a 1,2-dimethylbutyl group,and a 2,3-dimethylbutyl group. In light of the steric structure and thesynthesis yield of the complex, a methyl group, an ethyl group, anisopropyl group, and a tert-butyl group are preferable; a methyl groupand a tert-butyl group are particularly preferable.

Here, in any of the above-described phosphorescent organometalliciridium complexes, the pyridyl group bonded to the 4-position of thepyrimidine skeleton preferably has a substituent at an ortho-position(R⁴ in the general formulas (G1), (G2), and (G3)). Such a structure ispreferable because orthometalation proceeds in a selective manner andthus the yield increases. In light of the steric structure and thesynthesis yield of the complex, the substituent is preferably a methylgroup, an ethyl group, or an isopropyl group, and a methyl group isparticularly preferable.

Next, specific structural formulae of the above-described phosphorescentorganometallic iridium complexes according to embodiments of the presentinvention will be shown (the following structural formulae (100) to(121)). Note that the present invention is not limited thereto.

Note that phosphorescent organometallic iridium complexes represented bythe structural formulae (100) to (121) are novel substances capable ofemitting phosphorescence. Note that there can be geometrical isomers andstereoisomers of these substances depending on the type of the ligand.The phosphorescent organometallic iridium complex according to oneembodiment of the present invention includes all of these isomers.

Next, an example of a method for synthesizing a phosphorescentorganometallic iridium complex represented by the general formula (G1)is described.

(Method for Synthesizing Phosphorescent Organometallic Iridium ComplexRepresented by General Formula (G1))

Step 1: Method for Synthesizing 3-Pyridyl Pyrimidine Derivative

First, an example of a method for synthesizing a 3-pyridyl pyrimidinederivative represented by the following general formula (G0) isdescribed.

In the general formula (G0), R¹ and R⁴ to R⁶ separately representhydrogen or an alkyl group having 1 to 6 carbon atoms; and R² and R³separately represent any of hydrogen, an alkyl group having 1 to 6carbon atoms, a phenyl group that may have a substituent, and a pyridylgroup that may have a substituent.

As illustrated in the following synthetic scheme (Q), the 3-pyridylpyrimidine derivative represented by the general formula (G0) can beobtained by coupling a boronic acid, a boronate ester, or acyclic-triolborate salt (A1) with a halogenated pyrimidine compound(A2). As the cyclic-triolborate salt, a lithium salt, a potassium salt,or a sodium salt may be used.

In the synthetic scheme (Q), X represents halogen; R¹ and R⁴ to R⁶separately represent hydrogen or an alkyl group having 1 to 6 carbonatoms; R² and R³ separately represent any of hydrogen, an alkyl grouphaving 1 to 6 carbon atoms, a phenyl group that may have a substituent,and a pyridyl group that may have a substituent; R³¹ represents any of asingle bond, a methylene group, an ethylidene group, a propylidenegroup, and an isopropylidene group; and R³² to R³⁵ may be the same ordifferent from one another, and represent a hydrogen atom or an alkylgroup having 1 to 3 carbon atoms. R³³ and R³⁵ may be bonded to eachother via a carbon chain to form a ring.

Alternatively, as illustrated in the following synthetic scheme (Q′),the 3-pyridyl pyrimidine derivative represented by the general formula(G0) can be obtained by reacting 1,3-diketone (A1′) of pyridyl withamidine (A2′).

In the synthetic scheme (Q′), R¹ and R⁴ to R⁶ separately representhydrogen or an alkyl group having 1 to 6 carbon atoms; and R² and R³separately represent any of hydrogen, an alkyl group having 1 to 6carbon atoms, a phenyl group that may have a substituent, and a pyridylgroup that may have a substituent.

Note that since a wide variety of compounds (A1), (A2), (A1′), and (A2′)are commercially available or their synthesis is feasible, a greatvariety of the 3-pyridyl pyrimidine derivative represented by thegeneral formula (G0) can be synthesized. Thus, one of features of thephosphorescent organometallic iridium complex according to oneembodiment of the present invention is the abundance of ligandvariation.

Step 2: Method for Synthesizing Phosphorescent Organometallic IridiumComplex Represented by General Formula (G1)

The phosphorescent organometallic iridium complex represented by thegeneral formula (G1) according to one embodiment of the presentinvention can be synthesized by mixing the 3-pyridyl pyrimidinederivative represented by the general formula (G0) obtained in the aboveStep 1 with an iridium compound containing halogen (e.g., iridiumchloride, iridium bromide, or iridium iodide,) or an iridium compound(e.g., an acetylacetonate complex or a diethylsulfide complex) and thenby heating the mixture. Note that this heating process may be performedafter the 3-pyridyl pyrimidine derivative represented by the generalformula (G0) and the iridium compound containing halogen or the iridiumcompound are dissolved in an alcohol-based solvent (e.g., glycerol,ethylene glycol, 2-methoxyethanol, or 2-ethoxyethanol). There is noparticular limitation on a heating means, and an oil bath, a sand bath,or an aluminum block may be used. Alternatively, microwaves can be usedas a heating means.

In a synthetic scheme (S), R¹ and R⁴ to R⁶ separately represent hydrogenor an alkyl group having 1 to 6 carbon atoms; and R² and R³ separatelyrepresent any of hydrogen, an alkyl group having 1 to 6 carbon atoms, aphenyl group that may have a substituent, and a pyridyl group that mayhave a substituent.

Next, an example of a method for synthesizing a phosphorescentorganometallic iridium complex represented by the general formula (G2)is described.

(Method for Synthesizing Phosphorescent Organometallic Iridium ComplexRepresented by General Formula (G2))

Step 1: Method for Synthesizing 3-Pyridyl Pyrimidine Derivative

Step 1 here is the same as the above-described Step 1 in the method forsynthesizing the phosphorescent organometallic iridium complexrepresented by the general formula (G1) and therefore the description isomitted.

Step 2: Method for Synthesizing Dinuclear Complex Represented by GeneralFormula (P)

A dinuclear complex represented by a general formula (P), which is anovel type of an organometallic complex including a halogen-bridgedstructure, can be obtained in the following manner. As illustrated in asynthetic scheme (T) below, the 3-pyridyl pyrimidine derivativerepresented by a general formula (G0) obtained in the above Step 1 andan iridium compound containing halogen (e.g., iridium chloride, iridiumbromide, or iridium iodide) are heated in an inert gas atmosphere inbulk, in an alcoholic solvent (e.g., glycerol, ethylene glycol,2-methoxyethanol, or 2-ethoxyethanol) alone, or in a mixed solvent ofwater and one or more of the alcoholic solvents. There is no particularlimitation on a heating means, and an oil bath, a sand bath, or analuminum block may be used. Alternatively, microwaves can be used as aheating means.

In the synthetic scheme (T), X represents halogen; R¹ and R⁴ to R⁶separately represent hydrogen or an alkyl group having 1 to 6 carbonatoms; and R² and R³ separately represent any of hydrogen, an alkylgroup having 1 to 6 carbon atoms, a phenyl group that may have asubstituent, and a pyridyl group that may have a substituent.

Step 3: Method for Synthesizing Phosphorescent Organometallic IridiumComplex Represented by General Formula (G2)

Next, as shown in the following synthetic scheme (U), the dinuclearcomplex represented by the general formula (P) obtained in the abovesynthetic scheme (T) is reacted with HL which is a material of amonoanionic ligand in an inert gas atmosphere, whereby a proton of HL isseparated and L coordinates to the central metal Ir. Thus, thephosphorescent organometallic iridium complex represented by the generalformula (G2) according to one embodiment of the present invention can beobtained. There is no particular limitation on a heating means, and anoil bath, a sand bath, or an aluminum block may be used. Alternatively,microwaves can be used as a heating means.

In the synthetic scheme (U), L represents a monoanionic ligand; Xrepresents halogen; R¹ and R⁴ to R⁶ separately represent hydrogen or analkyl group having 1 to 6 carbon atoms; and R² and R³ separatelyrepresent any of hydrogen, an alkyl group having 1 to 6 carbon atoms, aphenyl group that may have a substituent, and a pyridyl group that mayhave a substituent.

The above is the description of the example of a method for synthesizinga phosphorescent organometallic iridium complex according to oneembodiment of the present invention; however, the present invention isnot limited thereto and any other synthetic method may be employed.

Note that the above-described phosphorescent organometallic iridiumcomplex according to one embodiment of the present invention can emitphosphorescence and thus can be used as a light-emitting material or alight-emitting substance of a light-emitting element.

With the use of the phosphorescent organometallic iridium complexaccording to one embodiment of the present invention, a light-emittingelement, a light-emitting device, an electronic device, or a lightingdevice with high emission efficiency can be obtained. Further, alight-emitting element, a light-emitting device, an electronic device,or a lighting device with low power consumption can be obtained.

Note that the structure described in this embodiment can be used incombination with any of the structures described in the otherembodiments, as appropriate.

Embodiment 2

In this embodiment, a light-emitting element will be described withreference to FIG. 1. In the light-emitting element, the phosphorescentorganometallic iridium complex described in Embodiment 1 as oneembodiment of the present invention is used for a light-emitting layer.

In a light-emitting element described in this embodiment, as illustratedin FIG. 1, an EL layer 102 including a light-emitting layer 113 isprovided between a pair of electrodes (a first electrode (anode) 101 anda second electrode (cathode) 103), and the EL layer 102 includes ahole-injection layer 111, a hole-transport layer 112, anelectron-transport layer 114, an electron-injection layer 115, acharge-generation layer (E) 116, and the like in addition to thelight-emitting layer 113.

By voltage application to such a light-emitting element, holes injectedfrom the first electrode 101 side and electrons injected from the secondelectrode 103 side recombine in the light-emitting layer 113 to raisethe phosphorescent organometallic iridium complex to an excited state.Then, light is emitted when the phosphorescent organometallic iridiumcomplex in the excited state relaxes to the ground state. Thus, thephosphorescent organometallic iridium complex in one embodiment of thepresent invention functions as a light-emitting substance in thelight-emitting element.

The hole-injection layer 111 included in the EL layer 102 is a layercontaining a substance having a high hole-transport property and anacceptor substance. When electrons are extracted from the substancehaving a high hole-transport property owing to the acceptor substance,holes are generated. Thus, holes are injected from the hole-injectionlayer 111 into the light-emitting layer 113 through the hole-transportlayer 112.

The charge-generation layer (E) 116 contains a substance having a highhole-transport property and an acceptor substance. Electrons areextracted from the substance having a high hole-transport property owingto the acceptor substance, and the extracted electrons are injected fromthe electron-injection layer 115 having an electron-injection propertyinto the light-emitting layer 113 through the electron-transport layer114.

A specific example in which the light-emitting element described in thisembodiment is manufactured is described.

As the first electrode (anode) 101 and the second electrode (cathode)103, a metal, an alloy, an electrically conductive compound, a mixturethereof, and the like can be used. Specifically, indium oxide-tin oxide(indium tin oxide), indium oxide-tin oxide containing silicon or siliconoxide, indium oxide-zinc oxide (indium zinc oxide), indium oxidecontaining tungsten oxide and zinc oxide, gold (Au), platinum (Pt),nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe),cobalt (Co), copper (Cu), palladium (Pd), and titanium (Ti) can be used.In addition, an element belonging to Group 1 or Group 2 of the periodictable, for example, an alkali metal such as lithium (Li) or cesium (Cs),an alkaline earth metal such as calcium (Ca) or strontium (Sr),magnesium (Mg), an alloy containing such an element (e.g., MgAg orAlLi), a rare earth metal such as europium (Eu) or ytterbium (Yb), analloy containing such an element, graphene, and the like can be used.The first electrode (anode) 101 and the second electrode (cathode) 103can be formed by, for example, a sputtering method, an evaporationmethod (including a vacuum evaporation method), or the like.

As the substance having a high hole-transport property used for thehole-injection layer 111, the hole-transport layer 112, and thecharge-generation layer (E) 116, the following can be given, forexample: aromatic amine compounds such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB orα-NPD),N,N-bis(3-methylphenyl)-N,N-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD), 4,4′,4″-tris(carbazol-9-yl)triphenylamine(abbreviation: TCTA), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine(abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA), and4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB);3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1);3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2);3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1); and the like. Alternatively, the followingcarbazole derivative can be used: 4,4′-di(N-carbazolyl)biphenyl(abbreviation: CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl] benzene(abbreviation: TCPB), and 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole(abbreviation: CzPA). The substances mentioned here are mainly ones thathave a hole mobility of 10⁻⁶ cm²/V·s or higher. However, a substanceother than the above-described substances may also be used as long asthe hole-transport property is higher than the electron-transportproperty.

Further, a high molecular compound such as poly(N-vinylcarbazole)(abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), orpoly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (abbreviation:Poly-TPD) can be used.

As examples of the acceptor substance that is used for thehole-injection layer 111 and the charge-generation layer (E) 116, atransition metal oxide or an oxide of a metal belonging to any of Group4 to Group 8 of the periodic table can be given. Specifically,molybdenum oxide is particularly preferable.

The light-emitting layer 113 contains any of the phosphorescentorganometallic iridium complexes described in Embodiment 1 as a guestmaterial serving as a light-emitting substance and a substance that hashigher triplet excitation energy than this phosphorescent organometalliciridium complex as a host material.

Preferable examples of the substance (i.e., host material) used fordispersing the phosphorescent organometallic iridium complex are asfollows: compounds having an arylamine skeleton, such as4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation:PCBA1BP),3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1), 2,3-bis(4-diphenylaminophenyl)quinoxaline(abbreviation: TPAQn), and NPB; carbazole derivatives such as CBP and4,4′,4″-tris(N-carbazolyl)triphenylamine (abbreviation: TCTA);nitrogen-containing heteroaromatic compounds such as2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:2mDBTPDBq-II),2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[fh]quinoxaline(abbreviation: 2mDBTBPDBq-II),2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl] dibenzo[f,h]quinoxaline(abbreviation: 2CzPDBq-III); and metal complexes such asbis[2-(2-hydroxyphenyl)pyridinato]zinc (abbreviation: Znpp₂),bis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation: Zn(BOX)₂),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (abbreviation:BAlq), and tris(8-quinolinolato)aluminum (abbreviation: Alq₃).Alternatively, a high molecular compound such as PVK can be used.

Note that in the case where the light-emitting layer 113 contains theabove-described phosphorescent organometallic iridium complex (guestmaterial) and the host material, phosphorescence with high emissionefficiency can be obtained from the light-emitting layer 113.

The electron-transport layer 114 contains a substance having a highelectron-transport property. For the electron-transport layer 114, it ispossible to use a metal complex such as Alq₃,tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq₂), BAlq,Zn(BOX)₂, or bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation:Zn(BTZ)₂). Alternatively, a heteroaromatic compound such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl] benzene(abbreviation: OXD-7),3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen),bathocuproine (abbreviation: BCP), or4,4′-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs) can beused. Further alternatively, a high molecular compound such aspoly(2,5-pyridinediyl) (abbreviation: PPy),poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)](abbreviation: PF-Py) orpoly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)](abbreviation: PF-BPy) can be used. The substances mentioned here aremainly ones that have an electron mobility of 10⁻⁶ cm²/V·s or higher.Note that any substance other than the above substances may be used forthe electron-transport layer as long as the electron-transport propertyis higher than the hole-transport property.

Furthermore, the electron-transport layer is not limited to a singlelayer, and two or more layers made of the aforementioned substances maybe stacked.

The electron-injection layer 115 contains a substance having a highelectron-injection property. For the electron-injection layer 115, analkali metal, an alkaline earth metal, magnesium (Mg), or a compound ofany of the above metals such as lithium fluoride (LiF), cesium fluoride(CsF), calcium fluoride (CaF₂), or lithium oxide (LiO_(x)) can be used.Alternatively, a rare earth metal compound like erbium fluoride (ErF₃)can be used. Further alternatively, the above-described substances forforming the electron-transport layer 114 can be used.

Alternatively, a composite material in which an organic compound and anelectron donor (donor) are mixed may be used for the electron-injectionlayer 115. The composite material is superior in an electron-injectionproperty and an electron-transport property, since electrons aregenerated in the organic compound by the electron donor. In this case,the organic compound is preferably a material excellent in transportingthe generated electrons. Specifically, the above-described substancesfor forming the electron-transport layer 114 (e.g., a metal complex anda heteroaromatic compound) or the like can be used. As the electrondonor, any substance which shows an electron-donating property withrespect to the organic compound may be used. Preferable examples are analkali metal, an alkaline earth metal, and a rare earth metal.Specifically, lithium, cesium, calcium, erbium, ytterbium, and magnesiumcan be given. Further, an alkali metal oxide and an alkaline earth metaloxide are preferable, and a lithium oxide, a calcium oxide, a bariumoxide, and the like can be given. Alternatively, Lewis base such asmagnesium oxide can be used. Further alternatively, an organic compoundsuch as tetrathiafulvalene (abbreviation: TTF) can be used.

Note that each of the above-described hole-injection layer 111,hole-transport layer 112, light-emitting layer 113, electron-transportlayer 114, electron-injection layer 115, and charge-generation layer (E)116 can be formed by a method such as an evaporation method (e.g., avacuum evaporation method), an inkjet method, or a coating method.

In the above-described light-emitting element, current flows due to apotential difference generated between the first electrode 101 and thesecond electrode 103 and holes and electrons recombine in the EL layer102, so that light is emitted. Then, the emitted light is extractedoutside through one or both of the first electrode 101 and the secondelectrode 103. Therefore, one or both of the first electrode 101 and thesecond electrode 103 are electrodes having a light-transmittingproperty.

The above-described light-emitting element can emit phosphorescenceoriginating from the phosphorescent organometallic iridium complex andthus can have higher efficiency than a light-emitting element using afluorescent compound.

Note that the light-emitting element described in this embodiment is anexample of a light-emitting element manufactured using thephosphorescent organometallic iridium complex according to oneembodiment of the present invention. Further, as a structure of alight-emitting device including the above light-emitting element, apassive matrix type light-emitting device and an active matrix typelight-emitting device can be manufactured. It is also possible tomanufacture a light-emitting device with a microcavity structureincluding a light-emitting element which is different from the abovelight-emitting elements as described in another embodiment. Each of theabove light-emitting devices is included in the present invention.

Note that there is no particular limitation on a structure of the TFT inthe case of manufacturing the active matrix type light-emitting device.For example, a staggered TFT or an inverted staggered TFT can be used asappropriate. Further, a driver circuit formed over a TFT substrate maybe formed using both of an n-channel TFT and a p-channel TFT or onlyeither an n-channel TFT or a p-channel TFT. Furthermore, there is noparticular limitation on the crystallinity of a semiconductor film usedfor the TFT. For example, an amorphous semiconductor film, a crystallinesemiconductor film, an oxide semiconductor film, or the like can beused.

Note that the structure described in this embodiment can be used incombination with any of the structures described in the otherembodiments, as appropriate.

Embodiment 3

In this embodiment, as one embodiment of the present invention, alight-emitting element in which two or more kinds of organic compoundsas well as a phosphorescent organometallic iridium complex are used fora light-emitting layer will be described.

A light-emitting element described in this embodiment includes an ELlayer 203 between a pair of electrodes (an anode 201 and a cathode 202)as illustrated in FIG. 2. Note that the EL layer 203 includes at least alight-emitting layer 204 and may include a hole-injection layer, ahole-transport layer, an electron-transport layer, an electron-injectionlayer, a charge-generation layer (E), and the like. Note that for thehole-injection layer, the hole-transport layer, the electron-transportlayer, the electron-injection layer, and the charge-generation layer(E), the substances described in Embodiment 2 can be used.

The light-emitting layer 204 described in this embodiment contains aphosphorescent compound 205 using the phosphorescent organometalliciridium complex described in Embodiment 1, a first organic compound 206,and a second organic compound 207. Note that the phosphorescent compound205 is a guest material in the light-emitting layer 204. Moreover, oneof the first organic compound 206 and the second organic compound 207,the content of which is higher than that of the other in thelight-emitting layer 204, is a host material in the light-emitting layer204.

When the light-emitting layer 204 has the structure in which the guestmaterial is dispersed in the host material, crystallization of thelight-emitting layer can be suppressed. Further, it is possible tosuppress concentration quenching due to high concentration of the guestmaterial, and thus the light-emitting element can have higher emissionefficiency.

Note that it is preferable that a triplet excitation energy level (T₁level) of each of the first organic compound 206 and the second organiccompound 207 be higher than that of the phosphorescent compound 205.This is because, when the T₁ level of the first organic compound 206 (orthe second organic compound 207) is lower than that of thephosphorescent compound 205, the triplet excitation energy of thephosphorescent compound 205, which is to contribute to light emission,is quenched by the first organic compound 206 (or the second organiccompound 207) and accordingly the emission efficiency is decreased.

Here, for improvement in the efficiency of energy transfer from a hostmaterial to a guest material, Förster mechanism (dipole-dipoleinteraction) and Dexter mechanism (electron exchange interaction), whichare known as mechanisms of energy transfer between molecules, areconsidered. According to the mechanisms, it is preferable that anemission spectrum of a host material (a fluorescence spectrum in energytransfer from a singlet excited state, and a phosphorescence spectrum inenergy transfer from a triplet excited state) largely overlap with anabsorption spectrum of a guest material (specifically, a spectrum in anabsorption band on the longest wavelength (lowest energy) side).However, in general, it is difficult to obtain an overlap between afluorescence spectrum of a host material and an absorption spectrum inan absorption band on the longest wavelength (lowest energy) side of aguest material. The reason for this is as follows: if the fluorescencespectrum of the host material overlaps with the absorption spectrum inthe absorption band on the longest wavelength (lowest energy) side ofthe guest material, since a phosphorescence spectrum of the hostmaterial is located on a longer wavelength (lower energy) side than thefluorescence spectrum, the T₁ level of the host material becomes lowerthan the T₁ level of the phosphorescent compound and the above-describedproblem of quenching occurs; yet, when the host material is designed insuch a manner that the T₁ level of the host material is higher than theT₁ level of the phosphorescent compound to avoid the problem ofquenching, the fluorescence spectrum of the host material is shifted tothe shorter wavelength (higher energy) side, and thus the fluorescencespectrum does not have any overlap with the absorption spectrum in theabsorption band on the longest wavelength (lowest energy) side of theguest material. For that reason, in general, it is difficult to obtainan overlap between a fluorescence spectrum of a host material and anabsorption spectrum in an absorption band on the longest wavelength(lowest energy) side of a guest material so as to maximize energytransfer from a singlet excited state of a host material.

Thus, in this embodiment, a combination of the first organic compoundand the second organic compound preferably forms an exciplex (alsoreferred to as excited complex). In this case, the first organiccompound 206 and the second organic compound 207 form an exciplex at thetime of recombination of carriers (electrons and holes) in thelight-emitting layer 204. Thus, in the light-emitting layer 204, afluorescence spectrum of the first organic compound 206 and that of thesecond organic compound 207 are converted into an emission spectrum ofthe exciplex which is located on a longer wavelength side. Moreover,when the first organic compound and the second organic compound areselected in such a manner that the emission spectrum of the exciplexlargely overlaps with the absorption spectrum of the guest material,energy transfer from a singlet excited state can be maximized. Note thatalso in the case of a triplet excited state, energy transfer from theexciplex, not from the host material, is assumed to occur.

For the phosphorescent compound 205, the phosphorescent organometalliciridium complex described in Embodiment 1 is used. Although thecombination of the first organic compound 206 and the second organiccompound 207 can be determined such that an exciplex is formed, acombination of a compound which is likely to accept electrons (acompound having an electron-trapping property) and a compound which islikely to accept holes (a compound having a hole-trapping property) ispreferably employed.

As a compound which is likely to accept electrons, a π-electrondeficient heteroaromatic compound such as a nitrogen-containingheteroaromatic compound is preferable. For example, a quinoxalinederivative and a dibenzoquinoxaline derivative can be given and examplesthereof include 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II),2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II),2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[fh]quinoxaline(abbreviation: 2CzPDBq-III), 7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II),6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:6mDBTPDBq-II), and the like.

As a compound which is likely to accept holes, a π-electron richheteroaromatic compound (e.g., a carbazole derivative or an indolederivative) or an aromatic amine compound is preferable. For example,the following can be given:4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation:PCBA1BP),4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBNBB),3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1),4,4′,4″-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation:1′-TNATA),2,7-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-spiro-9,9′-bifluorene(abbreviation: DPA2SF),N,N′-bis(9-phenylcarbazol-3-yl)-N,N-diphenylbenzene-1,3-diamine(abbreviation: PCA2B),N-(9,9-dimethyl-2-diphenylamino-9H-fluoren-7-yl)diphenylamine(abbreviation: DPNF),N,N′,N″-triphenyl-N,N′,N″-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-triamine(abbreviation: PCA3B),2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9′-bifluorene(abbreviation: PCASF),2-[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9′-bifluorene(abbreviation: DPASF),N,N′-bis[4-(carbazol-9-yl)phenyl]-N,N′-diphenyl-9,9-dimethylfluorene-2,7-diamine(abbreviation: YGA2F),4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl (abbreviation: TPD),4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB),N-(9,9-dimethyl-9H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N′-phenyl-N′-(9,9-dimethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine(abbreviation: DFLADFL),3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1),3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzDPA1),3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzDPA2),4,4′-bis(N-{4-[N-(3-methylphenyl)-N-phenylamino]phenyl}-N-phenylamino)biphenyl(abbreviation: DNTPD),3,6-bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole(abbreviation: PCzTPN2), and3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2).

As for the above-described first and second organic compounds 206 and207, the present invention is not limited to the above examples. Thecombination is determined so that an exciplex can be formed, theemission spectrum of the exciplex overlaps with the absorption spectrumof the phosphorescent compound 205, and the peak of the emissionspectrum of the exciplex has a longer wavelength than the peak of theabsorption spectrum of the phosphorescent compound 205.

Note that in the case where a compound which is likely to acceptelectrons and a compound which is likely to accept holes are used forthe first organic compound 206 and the second organic compound 207,carrier balance can be controlled by the mixture ratio of the compounds.Specifically, the ratio of the first organic compound to the secondorganic compound is preferably 1:9 to 9:1.

In the light-emitting element described in this embodiment, energytransfer efficiency can be improved owing to energy transfer utilizingan overlap between an emission spectrum of an exciplex and an absorptionspectrum of a phosphorescent compound; accordingly, it is possible toachieve high external quantum efficiency of a light-emitting element.

Note that in another structure of the present invention, thelight-emitting layer 204 can be formed using a host molecule having ahole-trapping property and a host molecule having an electron-trappingproperty as the two kinds of organic compounds other than thephosphorescent compound 205 (guest material) so that a phenomenon (guestcoupled with complementary hosts: GCCH) occurs in which holes andelectrons are introduced to guest molecules existing in the two kinds ofhost molecules and the guest molecules are brought into an excitedstate.

At this time, the host molecule having a hole-trapping property and thehost molecule having an electron-trapping property can be respectivelyselected from the above-described compounds which are likely to acceptholes and the above-described compounds which are likely to acceptelectrons.

Note that although the light-emitting element described in thisembodiment is one structural example of a light-emitting element, alight-emitting element having another structure which is described inanother embodiment can also be used for a light-emitting deviceaccording to one embodiment of the present invention. Further, as alight-emitting device including the above light-emitting element, apassive matrix type light-emitting device and an active matrix typelight-emitting device can be manufactured. It is also possible tomanufacture a light-emitting device with a microcavity structureincluding a light-emitting element which is different from the abovelight-emitting elements as described in another embodiment. Each of theabove light-emitting devices is included in the present invention.

Note that there is no particular limitation on the structure of the TFTin the case of manufacturing the active matrix type light-emittingdevice. For example, a staggered TFT or an inverted staggered TFT can beused as appropriate. Further, a driver circuit formed over a TFTsubstrate may be formed using both of an n-channel TFT and a p-channelTFT or only either an n-channel TFT or a p-channel TFT. Furthermore,there is no particular limitation on the crystallinity of asemiconductor film used for the TFT. For example, an amorphoussemiconductor film, a crystalline semiconductor film, an oxidesemiconductor film, or the like can be used.

Note that the structure described in this embodiment can be used incombination with any of the structures described in the otherembodiments, as appropriate.

Embodiment 4

In this embodiment, as one embodiment of the present invention, alight-emitting element (hereinafter referred to as tandem light-emittingelement) in which a plurality of EL layers are included so that acharge-generation layer is sandwiched therebetween will be described.

A light-emitting element described in this embodiment is a tandemlight-emitting element including a plurality of EL layers (a first ELlayer 302(1) and a second EL layer 302(2)) between a pair of electrodes(a first electrode 301 and a second electrode 304) as illustrated inFIG. 3A.

In this embodiment, the first electrode 301 functions as an anode, andthe second electrode 304 functions as a cathode. Note that the firstelectrode 301 and the second electrode 304 can have structures similarto those described in Embodiment 2. In addition, although the pluralityof EL layers (the first EL layer 302(1) and the second EL layer 302(2))may have structures similar to that described in Embodiment 2, any ofthe EL layers may have a structure similar to that described inEmbodiment 2. In other words, the structures of the first EL layer302(1) and the second EL layer 302(2) may be the same or different fromeach other and can be similar to those described in Embodiment 2.

Further, a charge-generation layer (I) 305 is provided between theplurality of EL layers (the first EL layer 302(1) and the second ELlayer 302(2)). The charge-generation layer (I) 305 has a function ofinjecting electrons into one of the EL layers and injecting holes intothe other of the EL layers when voltage is applied between the firstelectrode 301 and the second electrode 304. In this embodiment, whenvoltage is applied such that the potential of the first electrode 301 ishigher than that of the second electrode 304, the charge-generationlayer (I) 305 injects electrons into the first EL layer 302(1) andinjects holes into the second EL layer 302(2).

Note that in terms of light extraction efficiency, the charge-generationlayer (I) 305 preferably has a light-transmitting property with respectto visible light (specifically, the charge-generation layer (I) 305 hasa visible light transmittance of 40% or more). Further, thecharge-generation layer (I) 305 functions even if it has lowerconductivity than the first electrode 301 or the second electrode 304.

The charge-generation layer (I) 305 may have either a structure in whichan electron acceptor (acceptor) is added to an organic compound having ahigh hole-transport property or a structure in which an electron donor(donor) is added to an organic compound having a high electron-transportproperty. Alternatively, both of these structures may be stacked.

In the case of the structure in which an electron acceptor is added toan organic compound having a high hole-transport property, as theorganic compound having a high hole-transport property, for example, anaromatic amine compound such as NPB, TPD, TDATA, MTDATA, or4,4′-bis[N-(Spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB), or the like can be used. The substances mentionedhere are mainly ones that have a hole mobility of 10⁻⁶ cm²/V·s orhigher. However, substances other than the above substances may be usedas long as they are organic compounds in which a hole-transport propertyis higher than an electron-transport property.

Further, as the electron acceptor,7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F₄-TCNQ), chloranil, and the like can be given. In addition, atransition metal oxide can be given. In addition, an oxide of metalsthat belong to Group 4 to Group 8 of the periodic table can be given.Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromiumoxide, molybdenum oxide, tungsten oxide, manganese oxide, and rheniumoxide are preferable since their electron-accepting property is high.Among these, molybdenum oxide is especially preferable since it isstable in the air, its hygroscopic property is low, and it is easilytreated.

On the other hand, in the case of the structure in which an electrondonor is added to an organic compound having a high electron-transportproperty, as the organic compound having a high electron-transportproperty, for example, a metal complex having a quinoline skeleton or abenzoquinoline skeleton, such as Alq, Almq₃, BeBq₂, or BAlq, or the likecan be used. Alternatively, a metal complex having an oxazole-basedligand or a thiazole-based ligand, such as Zn(BOX)₂ or Zn(BTZ)₂ can beused. Further alternatively, other than such a metal complex, PBD,OXD-7, TAZ, BPhen, BCP, or the like can be used. The substancesmentioned here are mainly ones that have an electron mobility of 10⁻⁶cm²/V·s or higher. Note that any substance other than the abovesubstances may be used as long as the electron-transport property ishigher than the hole-transport property.

Further, as the electron donor, an alkali metal, an alkaline earthmetal, a rare earth metal, a metal belonging to Group 13 of the periodictable, or an oxide or carbonate thereof can be used. Specifically,lithium (Li), cesium (Cs), magnesium (Mg), calcium (Ca), ytterbium (Yb),indium (In), lithium oxide, cesium carbonate, or the like is preferablyused. Alternatively, an organic compound such as tetrathianaphthacenemay be used as the electron donor.

Note that forming the charge-generation layer (I) 305 by using any ofthe above materials can suppress an increase in drive voltage caused bythe stack of the EL layers.

Although this embodiment shows the light-emitting element having two ELlayers, the present invention can be similarly applied to alight-emitting element in which n EL layers (n is three or more) arestacked as illustrated in FIG. 3B. In the case where a plurality of ELlayers are included between a pair of electrodes as in thelight-emitting element according to this embodiment, by provision of acharge-generation layer (I) between the EL layers, light emission in ahigh luminance region can be obtained with current density kept low.Since the current density can be kept low, the element can have a longlifetime. When the light-emitting element is used for lighting, voltagedrop due to resistance of an electrode material can be reduced, therebyachieving homogeneous light emission in a large area. Moreover, alight-emitting device of low power consumption, which can be driven at alow voltage, can be achieved.

Further, by forming EL layers to emit light of different colors fromeach other, a light-emitting element as a whole can provide lightemission of a desired color. For example, by forming a light-emittingelement having two EL layers such that the emission color of the firstEL layer and the emission color of the second EL layer are complementarycolors, the light-emitting element can provide white light emission as awhole. Note that the word “complementary” means color relationship inwhich an achromatic color is obtained when colors are mixed. That is,white light emission can be obtained by mixture of light fromsubstances, of which the light emission colors are complementary colors.

Further, the same can be applied to a light-emitting element havingthree EL layers. For example, the light-emitting element as a whole canprovide white light emission when the emission color of a first EL layeris red, the emission color of a second EL layer is green, and theemission color of a third EL layer is blue.

Note that the structure described in this embodiment can be used incombination with any of the structures described in the otherembodiments, as appropriate.

Embodiment 5

In this embodiment, as a light-emitting device utilizing phosphorescenceaccording to one embodiment of the present invention, a light-emittingdevice using a phosphorescent organometallic iridium complex will bedescribed.

A light-emitting device described in this embodiment has a micro opticalresonator (microcavity) structure in which a light resonant effectbetween a pair of electrodes is utilized. The light-emitting deviceincludes a plurality of light-emitting elements each of which has atleast an EL layer 405 between a pair of electrodes (a reflectiveelectrode 401 and a semi-transmissive and semi-reflective electrode 402)as illustrated in FIG. 4. Further, the EL layer 405 includes at least alight-emitting layer 404 serving as a light-emitting region and mayfurther include a hole-injection layer, a hole-transport layer, anelectron-transport layer, an electron-injection layer, acharge-generation layer (E), and the like. Note that the light-emittinglayer 404 contains a phosphorescent organometallic iridium complexaccording to one embodiment of the present invention.

In this embodiment, a light-emitting device is described which includeslight-emitting elements (a first light-emitting element (R) 410R, asecond light-emitting element (G) 410G, and a third light-emittingelement (B) 410B) having different structures as illustrated in FIG. 4.

The first light-emitting element (R) 410R has a structure in which afirst transparent conductive layer 403 a; an EL layer 405 including afirst light-emitting layer (B) 404B, a second light-emitting layer (G)404G, and a third light-emitting layer (R) 404R; and thesemi-transmissive and semi-reflective electrode 402 are sequentiallystacked over the reflective electrode 401. The second light-emittingelement (G) 410G has a structure in which a second transparentconductive layer 403 b, the EL layer 405, and the semi-transmissive andsemi-reflective electrode 402 are sequentially stacked over thereflective electrode 401. The third light-emitting element (B) 410B hasa structure in which the EL layer 405 and the semi-transmissive andsemi-reflective electrode 402 are sequentially stacked over thereflective electrode 401.

Note that the reflective electrode 401, the EL layer 405, and thesemi-transmissive and semi-reflective electrode 402 are common to thelight-emitting elements (the first light-emitting element (R) 410R, thesecond light-emitting element (G) 410G, and the third light-emittingelement (B) 410B). The first light-emitting layer (B) 404B emits light(λ_(B)) having a peak in a wavelength range from 420 nm to 480 nm. Thesecond light-emitting layer (G) 404G emits light (λ_(G)) having a peakin a wavelength range from 500 nm to 550 nm. The third light-emittinglayer (R) 404R emits light (λ_(R)) having a peak in a wavelength rangefrom 600 nm to 760 nm. Thus, in each of the light-emitting elements (thefirst light-emitting element (R) 410R, the second light-emitting element(G) 410G, and the third light-emitting element (B) 410B), light emittedfrom the first light-emitting layer (B) 404B, light emitted from thesecond light-emitting layer (G) 404G, and light emitted from the thirdlight-emitting layer (R) 404R overlap with each other; accordingly,light having a broad emission spectrum that covers a visible light rangecan be emitted. Note that the above wavelengths satisfy the relation ofλ_(B)<λ_(G)<λ_(R).

Each of the light-emitting elements described in this embodiment has astructure in which the EL layer 405 is interposed between the reflectiveelectrode 401 and the semi-transmissive and semi-reflective electrode402. Light emitted in all directions from the light-emitting layersincluded in the EL layer 405 is resonated by the reflective electrode401 and the semi-transmissive and semi-reflective electrode 402 whichfunction as a micro optical resonator (microcavity). Note that thereflective electrode 401 is formed using a conductive material havingreflectivity, and a film whose visible light reflectivity is 40% to100%, preferably 70% to 100%, and whose resistivity is 1×10⁻² Ωcm orlower is used. In addition, the semi-transmissive and semi-reflectiveelectrode 402 is formed using a conductive material having reflectivityand a conductive material having a light-transmitting property, and afilm whose visible light reflectivity is 20% to 80%, preferably 40% to70%, and whose resistivity is 1×10⁻² Ωcm or lower is used.

In this embodiment, the thicknesses of the transparent conductive layers(the first transparent conductive layer 403 a and the second transparentconductive layer 403 b) provided in the first light-emitting element (R)410R and the second light-emitting element (G) 410G, respectively, arevaried between the light-emitting elements, whereby the light-emittingelements differ in the optical path length from the reflective electrode401 to the semi-transmissive and semi-reflective electrode 402. In otherwords, in light having a broad emission spectrum, which is emitted fromthe light-emitting layers of each of the light-emitting elements, lightwith a wavelength that is resonated between the reflective electrode 401and the semi-transmissive and semi-reflective electrode 402 can beenhanced while light with a wavelength that is not resonatedtherebetween can be attenuated. Thus, when the elements differ in theoptical path length from the reflective electrode 401 to thesemi-transmissive and semi-reflective electrode 402, light withdifferent wavelengths can be extracted.

Note that the total thickness from the reflective electrode 401 to thesemi-transmissive and semi-reflective electrode 402 is set to mλ_(R)/2(m is a natural number) in the first light-emitting element (R) 410R;the total thickness from the reflective electrode 401 to thesemi-transmissive and semi-reflective electrode 402 is set to mλ_(G)/2(m is a natural number) in the second light-emitting element (G) 410G;and the total thickness from the reflective electrode 401 to thesemi-transmissive and semi-reflective electrode 402 is set to mλ_(B)/2(m is a natural number) in the third light-emitting element (B) 410B.

In this manner, the light (λ_(R)) emitted from the third light-emittinglayer (R) 404R included in the EL layer 405 is mainly extracted from thefirst light-emitting element (R) 410R, the light (λ_(G)) emitted fromthe second light-emitting layer (G) 404G included in the EL layer 405 ismainly extracted from the second light-emitting element (G) 410G, andthe light (λ_(B)) emitted from the first light-emitting layer (B) 404Bincluded in the EL layer 405 is mainly extracted from the thirdlight-emitting element (B) 410B. Note that the light extracted from eachof the light-emitting elements is emitted from the semi-transmissive andsemi-reflective electrode 402 side.

Further, strictly speaking, the total thickness from the reflectiveelectrode 401 to the semi-transmissive and semi-reflective electrode 402can be the total thickness from a reflection region in the reflectiveelectrode 401 to a reflection region in the semi-transmissive andsemi-reflective electrode 402. However, it is difficult to preciselydetermine the positions of the reflection regions in the reflectiveelectrode 401 and the semi-transmissive and semi-reflective electrode402; therefore, it is assumed that the above effect can be sufficientlyobtained wherever the reflection regions may be set in the reflectiveelectrode 401 and the semi-transmissive and semi-reflective electrode402.

Next, in the first light-emitting element (R) 410R, the optical pathlength from the reflective electrode 401 to the third light-emittinglayer (R) 404R is adjusted to a desired thickness ((2 m′+1)λ_(R)/4,where m′ is a natural number); thus, light emitted from the thirdlight-emitting layer (R) 404R can be amplified. Light (first reflectedlight) that is reflected by the reflective electrode 401 of the lightemitted from the third light-emitting layer (R) 404R interferes withlight (first incident light) that directly enters the semi-transmissiveand semi-reflective electrode 402 from the third light-emitting layer(R) 404R. Therefore, by adjusting the optical path length from thereflective electrode 401 to the third light-emitting layer (R) 404R tothe desired value ((2 m′+1)λ_(R)/4, where m′ is a natural number), thephases of the first reflected light and the first incident light can bealigned with each other and the light emitted from the thirdlight-emitting layer (R) 404R can be amplified.

Note that, strictly speaking, the optical path length from thereflective electrode 401 to the third light-emitting layer (R) 404R canbe the optical path length from a reflection region in the reflectiveelectrode 401 to a light-emitting region in the third light-emittinglayer (R) 404R. However, it is difficult to precisely determine thepositions of the reflection region in the reflective electrode 401 andthe light-emitting region in the third light-emitting layer (R) 404R;therefore, it is assumed that the above effect can be sufficientlyobtained wherever the reflection region and the light-emitting regionmay be set in the reflective electrode 401 and the third light-emittinglayer (R) 404R, respectively.

Next, in the second light-emitting element (G) 410E the optical pathlength from the reflective electrode 401 to the second light-emittinglayer (G) 404G is adjusted to a desired thickness ((2 m″+1)λ_(G)/4,where m″ is a natural number); thus, light emitted from the secondlight-emitting layer (G) 404G can be amplified. Light (second reflectedlight) that is reflected by the reflective electrode 401 of the lightemitted from the second light-emitting layer (G) 404G interferes withlight (second incident light) that directly enters the semi-transmissiveand semi-reflective electrode 402 from the second light-emitting layer(G) 404G. Therefore, by adjusting the optical path length from thereflective electrode 401 to the second light-emitting layer (G) 404G tothe desired value ((2 m″+1)λ_(G)/4, where m″ is a natural number), thephases of the second reflected light and the second incident light canbe aligned with each other and the light emitted from the secondlight-emitting, layer (G) 404G can be amplified.

Note that, strictly speaking, the optical path length from thereflective electrode 401 to the second light-emitting layer (G) 404G canbe the optical path length from a reflection region in the reflectiveelectrode 401 to a light-emitting region in the second light-emittinglayer (G) 404G. However, it is difficult to precisely determine thepositions of the reflection region in the reflective electrode 401 andthe light-emitting region in the second light-emitting layer (G) 404G;therefore, it is assumed that the above effect can be sufficientlyobtained wherever the reflection region and the light-emitting regionmay be set in the reflective electrode 401 and the second light-emittinglayer (G) 404G, respectively.

Next, in the third light-emitting element (B) 410B, the optical pathlength from the reflective electrode 401 to the first light-emittinglayer (B) 404B is adjusted to a desired thickness ((2 m′″+1)λ_(B)/4,where m′″ is a natural number); thus, light emitted from the firstlight-emitting layer (B) 404B can be amplified. Light (third reflectedlight) that is reflected by the reflective electrode 401 of the lightemitted from the first light-emitting layer (B) 404B interferes withlight (third incident light) that directly enters the semi-transmissiveand semi-reflective electrode 402 from the first light-emitting layer(B) 404B. Therefore, by adjusting the optical path length from thereflective electrode 401 to the first light-emitting layer (B) 404B tothe desired value ((2 m′″+1)λ_(B)/4, where m′″ is a natural number), thephases of the third reflected light and the third incident light can bealigned with each other and the light emitted from the firstlight-emitting layer (B) 404B can be amplified.

Note that, strictly speaking, the optical path length from thereflective electrode 401 to the first light-emitting layer (B) 404B inthe third light-emitting element can be the optical path length from areflection region in the reflective electrode 401 to a light-emittingregion in the first light-emitting layer (B) 404B. However, it isdifficult to precisely determine the positions of the reflection regionin the reflective electrode 401 and the light-emitting region in thefirst light-emitting layer (B) 404B; therefore, it is assumed that theabove effect can be sufficiently obtained wherever the reflection regionand the light-emitting region may be set in the reflective electrode 401and the first light-emitting layer (B) 404B, respectively.

Note that although each of the light-emitting elements in theabove-described structure includes a plurality of light-emitting layersin the EL layer, the present invention is not limited thereto; forexample, the structure of the tandem light-emitting element which isdescribed in Embodiment 4 can be combined, in which case a plurality ofEL layers are provided so that a charge-generation layer is sandwichedtherebetween in one light-emitting element and one or morelight-emitting layers are formed in each of the EL layers.

The light-emitting device described in this embodiment has a microcavitystructure, in which light with wavelengths which differ depending on thelight-emitting elements can be extracted even when they include the sameEL layers, so that it is not needed to form light-emitting elements forthe colors of R, G, and B. Therefore, the above structure isadvantageous for full color display owing to easiness in achievinghigher resolution display or the like. In addition, emission intensitywith a predetermined wavelength in the front direction can be increased,whereby power consumption can be reduced. The above structure isparticularly useful in the case of being used for a color display (imagedisplay device) including pixels of three or more colors but may also beused for lighting or the like.

Embodiment 6

In this embodiment, a light-emitting device including a light-emittingelement in which the phosphorescent organometallic iridium complex thatis one embodiment of the present invention is used in a light-emittinglayer will be described.

The light-emitting device may be either a passive matrix typelight-emitting device or an active matrix type light-emitting device.Note that any of the light-emitting elements described in the otherembodiments can be used for the light-emitting device described in thisembodiment.

In this embodiment, an active matrix type light-emitting device isdescribed with reference to FIGS. 5A and 5B.

Note that FIG. 5A is a top view illustrating a light-emitting device andFIG. 5B is a cross-sectional view taken along chain line A-A′ in FIG.5A. The active matrix type light-emitting device according to thisembodiment includes a pixel portion 502 provided over an elementsubstrate 501, a driver circuit portion (a source line driver circuit)503, and a driver circuit portion (a gate line driver circuit) 504. Thepixel portion 502, the driver circuit portion 503, and the drivercircuit portion 504 are sealed with a sealant 505 between the elementsubstrate 501 and a sealing substrate 506.

In addition, over the element substrate 501, a lead wiring 507 forconnecting an external input terminal, through which a signal (e.g., avideo signal, a clock signal, a start signal, a reset signal, or thelike) or electric potential from the outside is transmitted to thedriver circuit portion 503 and the driver circuit portion 504, isprovided. Here, an example is described in which a flexible printedcircuit (FPC) 508 is provided as the external input terminal. Althoughonly the FPC is illustrated here, a printed wiring board (PWB) may beattached to the FPC. The light-emitting device in the presentspecification includes, in its category, not only the light-emittingdevice itself but also the light-emitting device provided with the FPCor the PWB.

Next, a cross-sectional structure is explained with reference to FIG.5B. The driver circuit portion and the pixel portion are formed over theelement substrate 501; here are illustrated the driver circuit portion503 which is the source line driver circuit and the pixel portion 502.

An example is illustrated in which a CMOS circuit which is a combinationof an n-channel TFT 509 and a p-channel TFT 510 is formed as the drivercircuit portion 503. Note that a circuit included in the driver circuitportion may be formed using various CMOS circuits, PMOS circuits, orNMOS circuits. Although a driver integrated type in which the drivercircuit is formed over the substrate is described in this embodiment,the driver circuit is not necessarily formed over the substrate, and thedriver circuit can be formed outside the substrate.

The pixel portion 502 is formed of a plurality of pixels each of whichincludes a switching TFT 511, a current control TFT 512, and a firstelectrode (anode) 513 which is electrically connected to a wiring (asource electrode or a drain electrode) of the current control TFT 512.Note that an insulator 514 is formed to cover end portions of the firstelectrode (anode) 513. In this embodiment, the insulator 514 is formedusing a positive photosensitive acrylic resin.

In addition, in order to obtain favorable coverage by a film which is tobe stacked over the insulator 514, the insulator 514 is preferablyformed so as to have a curved surface with curvature at an upper edgeportion or a lower edge portion. For example, in the case of using apositive photosensitive acrylic resin as a material for the insulator514, the insulator 514 is preferably formed so as to have a curvedsurface with a curvature radius (0.2 μm to 3 μm) at the upper edgeportion. The insulator 514 can be formed using either a negativephotosensitive resin or a positive photosensitive resin. It is possibleto use, without limitation to an organic compound, either an organiccompound or an inorganic compound such as silicon oxide or siliconoxynitride.

An EL layer 515 and a second electrode (cathode) 516 are stacked overthe first electrode (anode) 513. In the EL layer 515, at least alight-emitting layer is provided which contains the phosphorescentorganometallic iridium complex according to one embodiment of thepresent invention. Further, in the EL layer 515, a hole-injection layer,a hole-transport layer, an electron-transport layer, anelectron-injection layer, a charge-generation layer, and the like can beprovided as appropriate in addition to the light-emitting layer.

Note that a light-emitting element 517 is formed of a stacked structureof the first electrode (anode) 513, the EL layer 515, and the secondelectrode (cathode) 516. For the first electrode (anode) 513, the ELlayer 515, and the second electrode (cathode) 516, the materialsdescribed in Embodiment 2 can be used. Although not illustrated, thesecond electrode (cathode) 516 is electrically connected to an FPC 508which is an external input terminal.

In addition, although the cross-sectional view of FIG. 5B illustratesonly one light-emitting element 517, a plurality of light-emittingelements are arranged in matrix in the pixel portion 502. Light-emittingelements that emit light of three kinds of colors (R, and B) areselectively formed in the pixel portion 502, so that a light-emittingdevice capable of full color display can be obtained. Alternatively, alight-emitting device which is capable of full color display may bemanufactured by a combination with color filters.

Further, the sealing substrate 506 is attached to the element substrate501 with the sealant 505, so that a light-emitting element 517 isprovided in a space 518 surrounded by the element substrate 501, thesealing substrate 506, and the sealant 505. Note that the space 518 maybe filled with an inert gas (such as nitrogen and argon) or the sealant505.

An epoxy-based resin is preferably used for the sealant 505. A materialused for these is desirably a material which does not transmit moistureor oxygen as much as possible. As the sealing substrate 506, a plasticsubstrate formed of fiberglass-reinforced plastics (FRP), polyvinylfluoride (PVF), polyester, acrylic, or the like can be used besides aglass substrate or a quartz substrate.

As described above, the active matrix type light-emitting device can beobtained.

Note that the structure described in this embodiment can be used incombination with any of the structures described in the otherembodiments, as appropriate.

Embodiment 7

In this embodiment, examples of a variety of electronic devices whichare completed using a light-emitting device will be described withreference to FIGS. 6A to 6D and FIGS. 7A to 7C. The phosphorescentorganometallic iridium complex according to one embodiment of thepresent invention is used for the light-emitting devices.

Examples of the electronic devices in which the light-emitting device isused are television devices (also referred to as TV or televisionreceivers), monitors for computers and the like, cameras such as digitalcameras and digital video cameras, digital photo frames, cellular phones(also referred to as portable telephone devices), portable gamemachines, portable information terminals, audio playback devices, largegame machines such as pin-ball machines, and the like. Specific examplesof these electronic devices are shown in FIGS. 6A to 6D.

FIG. 6A illustrates an example of a television device. In a televisiondevice 7100, a display portion 7103 is incorporated in a housing 7101.Images can be displayed by the display portion 7103, and thelight-emitting device can be used for the display portion 7103. Inaddition, here, the housing 7101 is supported by a stand 7105.

The television device 7100 can be operated by an operation switch of thehousing 7101 or a separate remote controller 7110. With operation keys7109 of the remote controller 7110, channels and volume can becontrolled and images displayed on the display portion 7103 can becontrolled. Furthermore, the remote controller 7110 may be provided witha display portion 7107 for displaying data output from the remotecontroller 7110.

Note that the television device 7100 is provided with a receiver, amodem, and the like. With the receiver, a general television broadcastcan be received. Furthermore, when the television device 7100 isconnected to a communication network by wired or wireless connection viathe modem, one-way (from a transmitter to a receiver) or two-way(between a transmitter and a receiver, between receivers, or the like)data communication can be performed.

FIG. 6B illustrates a computer, which includes a main body 7201, ahousing 7202, a display portion 7203, a keyboard 7204, an externalconnection port 7205, a pointing device 7206, and the like. Thiscomputer is manufactured by using a light-emitting device for thedisplay portion 7203.

FIG. 6C illustrates a portable game machine having two housings, ahousing 7301 and a housing 7302, which are connected with a jointportion 7303 so that the portable game machine can be opened or folded.A display portion 7304 is incorporated in the housing 7301 and a displayportion 7305 is incorporated in the housing 7302. In addition, theportable game machine illustrated in FIG. 6C includes a speaker portion7306, a recording medium insertion portion 7307, an LED lamp 7308, aninput unit (an operation key 7309, a connection terminal 7310, a sensor7311 (sensor having a function of measuring force, displacement,position, speed, acceleration, angular velocity, rotational frequency,distance, light, liquid, magnetism, temperature, chemical substance,sound, time, hardness, electric field, current, voltage, electric power,radiation, flow rate, humidity, gradient, oscillation, odor, or infraredrays), or a microphone 7312), and the like. It is needless to say thatthe structure of the portable game machine is not limited to the aboveas long as a light-emitting device is used for at least either thedisplay portion 7304 or the display portion 7305, or both, and mayinclude other accessories as appropriate. The portable game machineillustrated in FIG. 6C has a function of reading a program or datastored in a recording medium to display it in the display portion, and afunction of sharing information with another portable game machine bywireless communication. Note that the functions of the portable gamemachine illustrated in FIG. 6C are not limited to these functions, andthe portable amusement machine can have various functions.

FIG. 6D illustrates an example of a cellular phone. A cellular phone7400 is provided with a display portion 7402 incorporated in a housing7401, operation buttons 7403, an external connection port 7404, aspeaker 7405, a microphone 7406, and the like. Note that the cellularphone 7400 is manufactured using a light-emitting device for the displayportion 7402.

When the display portion 7402 of the cellular phone 7400 illustrated inFIG. 6D is touched with a finger or the like, data can be input into thecellular phone 7400. Further, operations such as making a call andcreating e-mail can be performed by touch on the display portion 7402with a finger or the like.

There are mainly three screen modes of the display portion 7402. Thefirst mode is a display mode mainly for displaying images. The secondmode is an input mode mainly for inputting data such as text. The thirdmode is a display-and-input mode in which two modes of the display modeand the input mode are combined.

For example, in the case of making a call or creating e-mail, a textinput mode mainly for inputting text is selected for the display portion7402 so that text displayed on a screen can be inputted. In this case,it is preferable to display a keyboard or number buttons on almost theentire screen of the display portion 7402.

When a detection device including a sensor for detecting inclination,such as a gyroscope or an acceleration sensor, is provided inside thecellular phone 7400, display on the screen of the display portion 7402can be automatically changed by determining the orientation of thecellular phone 7400 (whether the cellular phone is placed horizontallyor vertically for a landscape mode or a portrait mode).

The screen modes are switched by touching the display portion 7402 oroperating the operation buttons 7403 of the housing 7401. Alternatively,the screen modes can be switched depending on kinds of images displayedon the display portion 7402. For example, when a signal of an imagedisplayed on the display portion is a signal of moving image data, thescreen mode is switched to the display mode. When the signal is a signalof text data, the screen mode is switched to the input mode.

Moreover, in the input mode, when input by touching the display portion7402 is not performed within a specified period while a signal detectedby an optical sensor in the display portion 7402 is detected, the screenmode may be controlled so as to be switched from the input mode to thedisplay mode.

The display portion 7402 may also function as an image sensor. Forexample, an image of a palm print, a fingerprint, or the like is takenby touch on the display portion 7402 with the palm or the finger,whereby personal authentication can be performed. Further, by providinga backlight or a sensing light source which emits a near-infrared lightin the display portion, an image of a finger vein, a palm vein, or thelike can be taken.

FIGS. 7A and 7B illustrate a tablet terminal that can be folded. In FIG.7A, the tablet terminal is opened, and includes a housing 9630, adisplay portion 9631 a, a display portion 9631 b, a display-modeswitching button 9034, a power button 9035, a power-saving-modeswitching button 9036, a clip 9033, and an operation button 9038. Thetablet terminal is manufactured using the light-emitting device for oneor both of the display portion 9631 a and the display portion 9631 b.

A touch panel area 9632 a can be provided in a part of the displayportion 9631 a, in which area, data can be input by touching displayedoperation keys 9637. Note that FIG. 7A shows, as an example, that halfof the area of the display portion 9631 a has only a display functionand the other half of the area has a touch panel function. However, thestructure of the display portion 9631 a is not limited to this, and allthe area of the display portion 9631 a may have a touch panel function.For example, all the area of the display portion 9631 a can displaykeyboard buttons and serve as a touch panel while the display portion9631 b can be used as a display screen.

Like the display portion 9631 a, part of the display portion 9631 b canbe a touch panel area 9632 b. When a finger, a stylus, or the liketouches the place where a keyboard-display switching button 9639 isdisplayed in the touch panel, keyboard buttons can be displayed on thedisplay portion 9631 b.

Touch input can be performed concurrently on the touch panel areas 9632a and 9632 b.

The display-mode switching button 9034 can switch display orientation(e.g., between landscape mode and portrait mode) and select a displaymode (switch between monochrome display and color display), for example.With the power-saving-mode switching button 9036, the luminance ofdisplay can be optimized in accordance with the amount of external lightat the time when the tablet terminal is in use, which is detected withan optical sensor incorporated in the tablet terminal. The tabletterminal may include another detection device such as a sensor fordetecting orientation (e.g., a gyroscope or an acceleration sensor) inaddition to the optical sensor.

Although the display portion 9631 a and the display portion 9631 b havethe same display area in FIG. 7A, one embodiment of the presentinvention is not limited to this example. The display portion 9631 a andthe display portion 9631 b may have different areas or different displayquality. For example, one of them may be a display panel that candisplay higher-definition images than the other.

FIG. 7B illustrates the tablet terminal folded, which includes thehousing 9630, a solar battery 9633, a charge and discharge controlcircuit 9634, a battery 9635, and a DCDC converter 9636. Note that FIG.7B shows an example in which the charge and discharge control circuit9634 includes the battery 9635 and the DCDC converter 9636.

Since the tablet terminal can be folded in two, the housing 9630 can beclosed when the tablet terminal is not in use. Thus, the displayportions 9631 a and 9631 b can be protected, thereby providing a tabletterminal with high endurance and high reliability for long-term use.

The tablet terminal illustrated in FIGS. 7A and 7B can have otherfunctions such as a function of displaying various kinds of data (e.g.,a still image, a moving image, and a text image), a function ofdisplaying a calendar, a date, the time, or the like on the displayportion, a touch-input function of operating or editing the datadisplayed on the display portion by touch input, and a function ofcontrolling processing by various kinds of software (programs).

The solar battery 9633, which is attached on the surface of the tabletterminal, supplies electric power to a touch panel, a display portion,an image signal processor, and the like. Note that the solar battery9633 can be provided on one or both surfaces of the housing 9630, sothat the battery 9635 can be charged efficiently, which is preferable.When a lithium ion battery is used as the battery 9635, there is anadvantage of downsizing or the like.

The structure and operation of the charge and discharge control circuit9634 illustrated in FIG. 7B are described with reference to a blockdiagram of FIG. 7C. FIG. 7C illustrates the solar battery 9633, thebattery 9635, the DCDC converter 9636, a converter 9638, switches SW1 toSW3, and the display portion 9631. The battery 9635, the DCDC converter9636, the converter 9638, and the switches SW1 to SW3 correspond to thecharge and discharge control circuit 9634 in FIG. 7B.

First, an example of operation in the case where power is generated bythe solar battery 9633 using external light is described. The voltage ofpower generated by the solar battery is raised or lowered by the DCDCconverter 9636 so that the power has a voltage for charging the battery9635. When the display portion 9631 is operated with the power from thesolar battery 9633, the switch SW1 is turned on and the voltage of thepower is raised or lowered by the converter 9638 to a voltage needed foroperating the display portion 9631. In addition, when display on thedisplay portion 9631 is not performed, the switch SW1 is turned off anda switch SW2 is turned on so that charge of the battery 9635 may beperformed.

Here, the solar battery 9633 is shown as an example of a powergeneration means; however, there is no particular limitation on a way ofcharging the battery 9635, and the battery 9635 may be charged withanother power generation means such as a piezoelectric element or athermoelectric conversion element (Peltier element). For example, thebattery 9635 may be charged with a non-contact power transmission modulethat transmits and receives power wirelessly (without contact) to chargethe battery or with a combination of other charging means.

It is needless to say that one embodiment of the present invention isnot limited to the electronic device illustrated in FIGS. 7A to 7C aslong as the display portion described in the above embodiment isincluded.

As described above, the electronic devices can be obtained by using thelight-emitting device according to one embodiment of the presentinvention. Application range of the light-emitting device is so widethat the light-emitting device can be applied to electronic devices in avariety of fields.

Note that the structure described in this embodiment can be used incombination with any of the structures described in the otherembodiments, as appropriate.

Embodiment 8

In this embodiment, examples of a lighting device in which alight-emitting device including the phosphorescent organometalliciridium complex according to one embodiment of the present invention isused will be described with reference to FIG. 8.

FIG. 8 illustrates an example in which the light-emitting device is usedas an indoor lighting device 8001. Note that since the area of thelight-emitting device can be increased, a lighting device having a largearea can also be formed. In addition, a lighting device 8002 in which alight-emitting region has a curved surface can also be obtained with theuse of a housing with a curved surface. A light-emitting elementincluded in the light-emitting device described in this embodiment is ina thin film form, which allows the housing to be designed more freely.Therefore, the lighting device can be elaborately designed in a varietyof ways. Further, a wall of the room may be provided with a largelighting device 8003.

Moreover, when the light-emitting device is used for a table by beingused as a surface of a table, a lighting device 8004 which has afunction as a table can be obtained. When the light-emitting device isused as part of other furniture, a lighting device which has a functionas the furniture can be obtained.

In this manner, a variety of lighting devices in which thelight-emitting device is used can be obtained. Note that such lightingdevices are also embodiments of the present invention.

Note that the structure described in this embodiment can be used incombination with any of the structures described in the otherembodiments, as appropriate.

Example 1 Synthetic Example 1

This example shows a method for synthesizing the phosphorescentorganometallic iridium complexbis[2-methyl-3-(6-tert-butyl-4-pyrimidinyl-κN3)pyridyl-κC4](2,4-pentanedionato-κ²O,O′)iridium(III) (abbreviation:[Ir(tBumpypm)₂(acac)]) represented by the structural formula (100) inEmbodiment 1 according to one embodiment of the present invention. Astructure of [Ir(tBumpypm)₂(acac)] (abbreviation) is shown below.

Step 1: Synthesis of 4-Hydroxy-6-tert-butylpyrimidine

First, 7.2 g of formamidine acetate, 7.5 g of sodium methoxide, and 70mL of methanol were put in a 100 mL three-neck flask. Then, 10 g ofmethyl 4,4-dimethyloxovalerate was added to this mixed solution. Themixture was stirred at room temperature for 24 hours. After apredetermined time elapsed, a mixed solution of 17 mL of water and 7.2mL of acetic acid was added to the mixture, and the mixture was stirredat room temperature. This mixture was condensed, and the given residuewas dissolved in water. The solution was subjected to extraction withethyl acetate. The obtained solution of the extract was washed withsaturated brine, and anhydrate magnesium sulfate was added to theorganic layer for drying. The obtained mixture was subjected to gravityfiltration, and the filtrate was condensed to give a solid. This solidwas washed with ethyl acetate to give 4-hydroxy-6-tert-butylpyrimidine(white solid, yield of 49%). A synthetic scheme of Step 1 is shown in(a-1) below.

Step 2: Synthesis of 4-Chloro-6-tert-butylpyrimidine

Next, 4.7 g of 4-hydroxy-6-tert-butylpyrimidine obtained in Step 1 and14 mL of phosphoryl chloride were put in a 50 mL three-neck flask, andthe mixture was heated and refluxed for 1.5 hours. After the reflux,phosphoryl chloride was distilled off under reduced pressure. Theobtained residue was dissolved in dichloromethane, and washed with waterand then a saturated aqueous solution of sodium hydrogen carbonate.Anhydrate magnesium sulfate was added to the obtained organic layer fordrying. This mixture was subjected to gravity filtration, and thefiltrate was condensed to give a solid. This solid was purified bysilica gel column chromatography. As a developing solvent, a mixedsolvent of hexane and ethyl acetate in a ratio of 10:1 (v/v) was used.The obtained fraction was condensed to give4-chloro-6-tert-butylpyrimidine (white solid, yield of 78%). A syntheticscheme of Step 2 is shown in (a-2) below.

Step 3: Synthesis of 4-(2-Methylpyridin-3-yl)-6-tert-butylpyrimidine(abbreviation: HtBumpypm)

Next, 2.0 g of 4-chloro-6-tert-butylpyrimidine obtained in Step 2, 3.0 gof 2-methylpyridine-3-boronic acid pinacol ester, 17 mL of 1M aqueoussolution of potassium acetate, 17 mL of 1M aqueous solution of sodiumcarbonate, and 40 mL of acetonitrile were put in a 100 mL round-bottomflask, and the air in the flask was replaced with argon. To thismixture, 0.78 g of tetrakis(triphenylphosphine)palladium(0) was added,and the mixture was irradiated with microwaves under conditions of 100°C. and 100 W for 1 hour to cause a reaction. This reaction mixture wasextracted with ethyl acetate, and washing with saturated brine wasperformed. Anhydrous magnesium sulfate was added to the obtainedsolution of the extract for drying, and the resulting mixture wasgravity-filtered to give a filtrate. The resulting filtrate wasdissolved in a mixed solvent of ethyl acetate and hexane, and themixture was filtered through Celite, alumina, and Celite. The resultingfiltrate was purified by silica gel column chromatography. As adeveloping solvent, a mixed solvent of hexane and ethyl acetate in aratio of 3:2 (v/v) was used. The obtained fractions were condensed togive an oily substance. This oily substance was dissolved in a mixedsolvent of hexane and ethyl acetate, and the solution was filteredthrough a filter aid in which Celite, alumina, and Celite were stackedin this order. The resulting filtrate was condensed to give4-(2-methylpyridin-3-yl)-6-tert-butylpyrimidine (abbreviation:HtBumpypm) (light-yellow oily substance, yield of 92%). A syntheticscheme of Step 3 is shown in (a-3) below.

Step 4: Synthesis ofDi-μ-chloro-tetrakis[2-methyl-3-(6-tert-butyl-4-pyrimidinyl-κN3)pyridyl-κC4]diiridium(III) (abbreviation: [Ir(tBumpypm)₂Cl]₂)

Next, 2.0 g of the ligand HtBumpypm obtained in the above Step 3, 1.1 gof iridium chloride, 21 mL of 2-ethoxyethanol, and 7 mL of water wereput in a 50 mL recovery flask, and the air in the flask was replacedwith argon. This reaction container was heated by irradiation withmicrowaves under conditions of 100° C. and 100 W for 1 hour to cause areaction. After a predetermined time elapsed, the obtained reactionsolution was condensed to give a dinuclear complex [Ir(tBumpypm)₂Cl]₂(orange oily substance, yield of 100%). A synthetic scheme of Step 4 isshown in (a-4) below.

Step 5: Synthesis ofBis[2-methyl-3-(6-tert-butyl-4-pyrimidinyl-κN3)pyridyl-κC4](2,4-pentanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(tBumpypm)₂(acac)])

Next, 2.5 g of the dinuclear complex [Ir(tBumpypm)₂Cl]₂ obtained in theabove Step 4, 1.9 g of sodium carbonate, 0.55 g of acetylacetone, and 20mL of 2-ethoxyethanol were put in a 100 mL round-bottom flask, and theair in the flask was replaced with argon. This reaction container wasirradiated with microwaves under conditions of 100° C. and 120 W for 1hour to cause a reaction. After a predetermined time elapsed, theobtained reaction mixture was condensed, and ethanol was added theretoto give a sediment. This mixture was suction-filtered, and the resultingsolid was washed with ethanol to give the phosphorescent organometalliciridium complex [Ir(tBumpypm)₂(acac)] according to one embodiment of thepresent invention (yellow powder, yield of 24%). A synthetic scheme ofStep 5 is shown in (a-5) below.

Results of analysis of the yellow powder obtained in the above Step 5 bynuclear magnetic resonance spectrometry (¹H-NMR) are shown below. The¹H-NMR chart is shown in FIG. 9. These results revealed that thephosphorescent organometallic iridium complex [Ir(tBumpypm)₂(acac)](abbreviation) represented by the structural formula (100) according toone embodiment of the present invention was obtained in SyntheticExample 1.

¹H-NMR. δ (CDCl₃): 1.52 (s, 18H), 1.81 (s, 6H), 2.89 (s, 6H), 5.3 (s,1H), 6.09 (d, 2H), 6.54 (d, 2H), 8.08 (s, 2H), 9.06 (d, 2H).

Next, an analysis of [Ir(tBumpypm)₂(acac)] (abbreviation) was conductedby an ultraviolet-visible (UV) absorption spectrometry. The UV spectrumwas measured with an ultraviolet-visible spectrophotometer (V-550,produced by JASCO Corporation) using a dichloromethane solution (0.083mmol/L) at room temperature. Further, an emission spectrum of[Ir(tBumpypm)₂(acac)] (abbreviation) was measured. The emission spectrumwas measured with a fluorescence spectrophotometer (FS920, produced byHamamatsu Photonics K.K.) using a degassed dichloromethane solution(0.083 mmol/L) at room temperature. FIG. 10 shows the measurementresults. In FIG. 10, the horizontal axis represents wavelength and thevertical axes represent absorption intensity and emission intensity.

As shown in FIG. 10, the phosphorescent organometallic iridium complex[Ir(tBumpypm)₂(acac)] (abbreviation) according to one embodiment of thepresent invention has an emission peak at 511 nm, and green lightemission was observed from the dichloromethane solution.

Further,bis[2-methyl-3-(6-tert-butyl-4-pyrimidinyl-κN3)pyridyl-κC4](2,4-pentanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(tBumpypm)₂(acac)]) obtained in this example wasanalyzed by liquid chromatography mass spectrometry (LC/MS).

The LC/MS was carried out with Acquity UPLC (produced by WatersCorporation) and Xevo G2 T of MS (produced by Waters Corporation).

In the MS, ionization was carried out by an electrospray ionization(ESI) method. Capillary voltage and sample cone voltage were set to 3.0kV and 30 V, respectively. Detection was performed in a positive mode. Acomponent with m/z of 745 which underwent the separation and theionization under the above-mentioned conditions was collided with anargon gas in a collision cell to dissociate into fragment ions. Energy(collision energy) for the collision with argon was 30 eV. A mass rangefor the measurement was m/z=100-1200. The detection result of thedissociated fragment ions by time-of-flight (TOF) MS are shown in FIG.24.

The results in FIG. 24 show that product ions of the phosphorescentorganometallic iridium complex [Ir(tBumpypm)₂(acac)] (abbreviation)represented by the structural formula (100) according to one embodimentof the present invention were detected mainly around m/z=645, aroundm/z=358, and around m/z=228. Note that the results in FIG. 24 showscharacteristics derived from [Ir(tBumpypm)₂(acac)] (abbreviation) andtherefore can be regarded as important data for identifying[Ir(tBumpypm)₂(acac)] (abbreviation) contained in the mixture.

Example 2 Synthetic Example 2

This example shows a method for synthesizing the phosphorescentorganometallic iridium complex tris[2-methyl-3-(6-tert-butyl-4-pyrimidinyl-κN3)pyridyl-κC4]iridium(III)(abbreviation: [Ir(tBumpypm)₃]) represented by the structural formula(102) in Embodiment 1 according to one embodiment of the presentinvention. A structure of [Ir(tBumpypm)₃] is shown below.

Step 1: Synthesis of 4-Hydroxy-6-tert-butylpyrimidine

First, 7.2 g of formamidine acetate, 7.5 g of sodium methoxide, and 70mL of methanol were put in a 100 mL three-neck flask. Then, 10 g ofmethyl 4,4-dimethyloxovalerate was added to this mixed solution. Themixture was stirred at room temperature for 24 hours. After apredetermined time elapsed, a mixed solution of 17 mL of water and 7.2mL of acetic acid was added to the mixture, and the mixture was stirredat room temperature. This mixture was condensed, and the given residuewas dissolved in water. The solution was subjected to extraction withethyl acetate. The obtained solution of the extract was washed withsaturated brine, and anhydrate magnesium sulfate was added to theorganic layer for drying. The obtained mixture was subjected to gravityfiltration, and the filtrate was condensed to give a solid. This solidwas washed with ethyl acetate to give 4-hydroxy-6-tert-butylpyrimidine(white solid, yield of 49%). A synthetic scheme of Step 1 is shown in(b-1) below.

Step 2: Synthesis of 4-Chloro-6-tert-butylpyrimidine

Next, 4.7 g of 4-hydroxy-6-tert-butylpyrimidine obtained in Step 1 and14 mL of phosphoryl chloride were put in a 50 mL three-neck flask, andthe mixture was heated and refluxed for 1.5 hours. After the reflux,phosphoryl chloride was distilled off under reduced pressure. Theobtained residue was dissolved in dichloromethane, and washed with waterand then a saturated aqueous solution of sodium hydrogen carbonate.Anhydrate magnesium sulfate was added to the obtained organic layer fordrying. This mixture was subjected to gravity filtration, and thefiltrate was condensed to give a solid. This solid was purified bysilica gel column chromatography. As a developing solvent, a mixedsolvent of hexane and ethyl acetate in a ratio of 10:1 (v/v) was used.The obtained fraction was condensed to give4-chloro-6-tert-butylpyrimidine (white solid, yield of 78%). A syntheticscheme of Step 2 is shown in (b-2) below.

Step 3: Synthesis of 4-(2-Methylpyridin-3-yl)-6-tert-butylpyrimidine(abbreviation: HtBumpypm)

Next, 2.0 g of 4-chloro-6-tert-butylpyrimidine obtained in the aboveStep 2, 3.0 g of 2-methylpyridine-3-boronic acid pinacol ester, 17 mL of1M aqueous solution of potassium acetate, 17 mL of 1M aqueous solutionof sodium carbonate, and 40 mL of acetonitrile were put in a 100 mLround-bottom flask, and the air in the flask was replaced with argon. Tothis mixture, 0.78 g of tetrakis(triphenylphosphine)palladium(0) wasadded, and the mixture was irradiated with microwaves under conditionsof 100° C. and 100 W for 1 hour to cause a reaction. This reactionmixture was subjected to extraction with ethyl acetate, and washing withsaturated brine was performed. Anhydrous magnesium sulfate was added tothe obtained solution of the extract for drying, and the resultingmixture was gravity-filtered to give a filtrate. The resulting filtratewas dissolved in a mixed solvent of ethyl acetate and hexane, and themixture was filtered through Celite, alumina, and Celite. The resultingfiltrate was purified by silica gel column chromatography. As adeveloping solvent, a mixed solvent of hexane and ethyl acetate in aratio of 3:2 (v/v) was used. The obtained fractions were condensed togive an oily substance. This oily substance was dissolved in a mixedsolvent of hexane and ethyl acetate, and the solution was filteredthrough a filter aid in which Celite, alumina, and Celite were stackedin this order. The resulting filtrate was condensed to give4-(2-methylpyridin-3-yl)-6-tert-butylpyrimidine (abbreviation:HtBumpypm) (light-yellow oily substance, yield of 92%). A syntheticscheme of Step 3 is shown in (b-3) below.

Step 4: Synthesis of Tris[2-methyl-3-(6-tert-butyl-4-pyrimidinyl-κN3)pyridyl-κC4] iridium(III)(abbreviation: [Ir(tBumpypm)₃])

Next, 3.31 g of the ligand HtBumpypm obtained in the above Step 3, and1.42 g of tris(acetylacetonato)iridium(III) were put in a reactioncontainer provided with a three-way cock, and the air in the reactioncontainer was replaced with argon. After that, the mixture was heated at250° C. for 50.5 hours to cause a reaction. The obtained residue waspurified by flash column chromatography using ethyl acetate and methanolas a developing solvent in a ratio of 4:1. The solvent of the resultingfraction was distilled off to give a solid. The resulting solid wasrecrystallized twice from a mixed solvent of dichloromethane and hexaneto give the phosphorescent organometallic iridium complex[Ir(tBumpypm)₃] according to one embodiment of the present invention(yellow-brown powder, yield of 22%). A synthetic scheme of Step 4 isshown in (b-4) below.

Results of analysis of the yellow-brown powder obtained in the aboveStep 4 by nuclear magnetic resonance spectrometry (¹H-NMR) are shownbelow. The ¹H-NMR chart is shown in FIG. 11. These results revealed thatthe phosphorescent organometallic iridium complex [Ir(tBumpypm)₃](abbreviation) represented by the structural formula (102) according toone embodiment of the present invention was obtained in SyntheticExample 2.

¹H-NMR. δ (CDCl₃): 1.41 (s, 27H), 2.94 (s, 9H), 6.64 (d, 3H), 7.70 (d,3H), 8.12 (s, 3H), 8.24 (s, 3H).

Next, an analysis of [Ir(tBumpypm)₃] (abbreviation) was conducted by anultraviolet-visible (UV) absorption spectrometry. The UV spectrum wasmeasured with an ultraviolet-visible spectrophotometer (V-550, producedby JASCO Corporation) using a dichloromethane solution (0.080 mmol/L) atroom temperature. Further, an emission spectrum of [Ir(tBumpypm)₃](abbreviation) was measured. The emission spectrum was measured with afluorescence spectrophotometer (FS920, produced by Hamamatsu PhotonicsK.K.) using a degassed dichloromethane solution (0.080 mmol/L) at roomtemperature. FIG. 12 shows the measurement results. In FIG. 12, thehorizontal axis represents wavelength and the vertical axes representabsorption intensity and emission intensity.

As shown in FIG. 12, the phosphorescent organometallic iridium complex[Ir(tBumpypm)₃] (abbreviation) according to one embodiment of thepresent invention has an emission peak at 510 nm, and green lightemission was observed from the dichloromethane solution.

Further,tris[2-methyl-3-(6-tert-butyl-4-pyrimidinyl-κN3)pyridyl-κC4]iridium(III)(abbreviation: [Ir(tBumpypm)₃]) obtained in this example was analyzed byliquid chromatography mass spectrometry (LC/MS).

The LC/MS was carried out with Acquity UPLC (produced by WatersCorporation) and Xevo G2 T of MS (produced by Waters Corporation).

In the MS, ionization was carried out by an electrospray ionization(ESI) method. Capillary voltage and sample cone voltage were set to 3.0kV and 30 V, respectively. Detection was performed in a positive mode. Acomponent with m/z of 872 which underwent the separation and theionization under the above-mentioned conditions was collided with anargon gas in a collision cell to dissociate into fragment ions. Energy(collision energy) for the collision with argon was 30 eV. A mass rangefor the measurement was m/z=100-1200. The detection result of thedissociated fragment ions by time-of-flight (TOF) MS are shown in FIG.25.

The results in FIG. 25 show that product ions of the phosphorescentorganometallic iridium complex [Ir(tBumpypm)₃] (abbreviation)represented by the structural formula (102) according to one embodimentof the present invention were detected mainly around m/z=421 and aroundm/z=271. Note that the results in FIG. 25 shows characteristics derivedfrom [Ir(tBumpypm)₃] (abbreviation) and therefore can be regarded asimportant data for identifying [Ir(tBumpypm)₃] (abbreviation) containedin the mixture.

Example 3 Synthetic Example 3

This example shows a method for synthesizing the phosphorescentorganometallic iridium complexbis{3-[6-(2-methylpyridin-3-yl)-4-pyrimidinyl-κN3]-2-methylpyridyl-κC4}(2,4-pentane dionato-κ²O,O′)iridium(III) (abbreviation:[Ir(dmpypm)₂(acac)]) represented by the structural formula (101) inEmbodiment 1 according to one embodiment of the present invention. Astructure of [Ir(dmpypm)₂(acac)] (abbreviation) is shown below.

Step 1: Synthesis of 4-Chloro-6-(2-methylpyridin-3-yl)pyrimidine

First, 3.01 g of 4,6-dichloropyrimidine, 10.9 g of2-methylpyridine-3-boronic acid pinacol ester, 60 mL of 1M aqueoussolution of potassium acetate, 60 mL of 1M aqueous solution of sodiumcarbonate, and 60 mL of acetonitrile were put in a 300 mL three-neckflask, and the air in the flask was replaced with argon. To thismixture, 1.40 g of tetrakis(triphenylphosphine)palladium(0) was added,and the mixture was irradiated with microwaves under conditions of 70°C. and 400 W and for 2 hours to cause a reaction. This reaction mixturewas extracted with ethyl acetate, and washing with saturated brine wasperformed. Anhydrous magnesium sulfate was added to the obtainedsolution of the extract for drying, and the resulting mixture wasgravity-filtered to give a filtrate. A residue obtained by condensingthe filtrate was purified by flash column chromatography using ethylacetate as a developing solvent. A solid obtained by condensing thefraction was purified by flash column chromatography using hexane andethyl acetate in a ratio of 1:1 as a developing solvent, so that4-chloro-6-(2-methylpyridin-3-yl)pyrimidine was obtained (a yellow whitesolid, yield of 24%). A synthetic scheme of Step 1 is shown in (c-1)below.

Step 2: Synthesis of 4,6-Bis(2-methylpyridin-3-yl)pyrimidine

Next, 0.99 g of 4-chloro-6-(2-methylpyridin-3-yl)pyrimidine obtained inthe above Step 1, 1.34 g of 2-methylpyridine-3-boronic acid pinacolester, 7.2 mL of 1M aqueous solution of potassium acetate, 7.2 mL of 1Maqueous solution of sodium carbonate, and 15 mL of acetonitrile were putin a 100 mL round-bottom flask, and the air in the flask was replacedwith argon. To this mixture, 0.33 g oftetrakis(triphenylphosphine)palladium(0) was added, and the reactioncontainer was heated by being irradiated with microwaves (2.45 GHz, 100W) for 60 minutes. This reaction mixture was extracted with ethylacetate, and washing with saturated brine was performed. Anhydrousmagnesium sulfate was added to the obtained solution of the extract fordrying, and the resulting mixture was gravity-filtered to give afiltrate. A residue obtained by condensing the filtrate was purified byflash column chromatography using ethyl acetate and methanol in a ratioof 4:1 as a developing solvent, so that4,6-bis(2-methylpyridin-3-yl)pyrimidine (abbreviation: Hdmpypm) wasobtained (a yellow solid, yield of 93%). A synthetic scheme of Step 2 isshown in (c-2) below.

Step 3: Synthesis ofchloro-tetrakis{3-[6-(2-methylpyridin-3-yl)-4-pyrimidinyl-κN3]-2-methylpyridyl-κC4}diiridium(III)(abbreviation: [Ir(dmpypm)₂Cl]₂)

Next, 15 mL of 2-ethoxyethanol, 5 mL of water, 1.22 g of the ligandHdmpypm obtained in the above Step 2, and 0.66 g of iridium chloridehydrate (IrCl₃.H₂O) were put in a recovery flask equipped with a refluxpipe, and the air in the flask was replaced with argon. Then, microwaveirradiation (2.45 GHz, 100 W) was performed for 1 hour to cause areaction. The solvent was distilled off, and then the obtained residuewas suction-filtered and washed, so that a dinuclear complex[Ir(dmpypm)₂Cl]₂ was obtained (a brown solid, yield of 72%). A syntheticscheme of Step 3 is shown in (c-3) below.

Step 4: Synthesis ofBis{3-[6-(2-methylpyridin-3-yl)-4-pyrimidinyl-κN3]-2-methylpyridyl-κ4}(2,4-pentanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmpypm)₂(acac)])

Next, 1.18 g of the dinuclear complex [Ir(dmpypm)₂Cl]₂ obtained in theabove Step 3, 0.85 g of sodium carbonate, 0.24 g of acetylacetone, and30 mL of 2-ethoxyethanol were put in a 100 mL round-bottom flask, andthe air in the flask was replaced with argon. This reaction containerwas irradiated with microwaves under conditions of 110° C. and 120 W for1 hour. Further, 0.24 g of acetylacetone was added, and the reactioncontainer was irradiated with microwaves under conditions of 110° C. and120 W for 1 hour to cause a reaction. The solvent was distilled off, andthe obtained residue was suction-filtered with ethanol. The obtainedsolid was washed with water and ethanol. The obtained solid was purifiedby flash column chromatography using ethyl acetate as a developingsolvent. The fraction was condensed and the obtained solid wasrecrystallized from a mixed solvent of dichloromethane and hexane togive the phosphorescent organometallic iridium complex[Ir(dmpypm)₂(acac)] according to one embodiment of the present invention(yellow orange powder, yield of 11%). A synthetic scheme of Step 4 isshown in (c-4) below.

Results of analysis of the yellow orange powder obtained in the aboveStep 4 by nuclear magnetic resonance spectrometry (¹H-NMR) are shownbelow. The ¹H-NMR chart is shown in FIG. 13. These results revealed thatthe phosphorescent organometallic iridium complex [Ir(dmpypm)₂(acac)](abbreviation) represented by the structural formula (101) according toone embodiment of the present invention was obtained in SyntheticExample 3.

¹H-NMR. δ (CDCl₃): 1.88 (s, 6H), 2.89 (s, 6H), 2.94 (s, 6H), 5.38 (s,1H), 6.25 (d, 2H), 7.40 (dd, 2H), 7.62 (d, 2H), 8.06 (d, 2H), 8.27 (d,2H), 8.70 (d, 2H), 9.25 (d, 2H).

Next, an analysis of [Ir(dmpypm)₂(acac)] (abbreviation) was conducted byan ultraviolet-visible (UV) absorption spectrometry. The UV spectrum wasmeasured with an ultraviolet-visible spectrophotometer (V-550, producedby JASCO Corporation) using a dichloromethane solution (0.086 mmol/L) atroom temperature. Further, an emission spectrum of [Ir(dmpypm)₂(acac)](abbreviation) was measured. The emission spectrum was measured with afluorescence spectrophotometer (FS920, produced by Hamamatsu PhotonicsK.K.) using a degassed dichloromethane solution (0.086 mmol/L) at roomtemperature. FIG. 14 shows the measurement results. In FIG. 14, thehorizontal axis represents wavelength and the vertical axes representabsorption intensity and emission intensity.

As shown in FIG. 14, the phosphorescent organometallic iridium complex[Ir(dmpypm)₂(acac)] (abbreviation) according to one embodiment of thepresent invention has an emission peak at 551 nm, and yellow lightemission was observed from the dichloromethane solution.

Further,bis{3-[6-(2-methylpyridin-3-yl)-4-pyrimidinyl-κN3]-2-methylpyridyl-κC4}(2,4-pentanedionato-κ²O,O′)iridium(III) (abbreviation: [Ir(dmpypm)₂(acac)]) obtainedin this example was analyzed by liquid chromatography mass spectrometry(LC/MS).

The LC/MS was carried out with Acquity UPLC (produced by WatersCorporation) and Xevo G2 T of MS (produced by Waters Corporation).

In the MS, ionization was carried out by an electrospray ionization(ESI) method. Capillary voltage and sample cone voltage were set to 3.0kV and 30 V, respectively. Detection was performed in a positive mode. Acomponent with m/z of 814 which underwent the ionization under theabove-mentioned conditions was collided with an argon gas in a collisioncell to dissociate into product ions. Energy (collision energy) for thecollision with argon was 30 eV. A mass range for the measurement wasm/z=100-1200. The detection result of the dissociated fragment ions bytime-of-flight (TOF) MS are shown in FIG. 26.

The results in FIG. 24 show that product ions of the phosphorescentorganometallic iridium complex [Ir(dmpypm)₂(acac)] (abbreviation)represented by the structural formula (101) according to one embodimentof the present invention were detected mainly around m/z=715, aroundm/z=451, around m/z=358, and around m/z=263. Note that the results inFIG. 26 shows characteristics derived from [Ir(dmpypm)₂(acac)](abbreviation) and therefore can be regarded as important data foridentifying [Ir(dmpypm)₂(acac)] (abbreviation) contained in the mixture.

Example 4

In this example, a light-emitting element 1 in which the phosphorescentorganometallic iridium complexbis[2-methyl-3-(6-tert-butyl-4-pyrimidinyl-κN3)pyridyl-κC4](2,4-pentanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(tBumpypm)₂(acac)]) (the structural formula (100)) wasused for a light-emitting layer will be described with reference to FIG.15. Further, as a comparative element, a comparative light-emittingelement 1 was also fabricated in which a phosphorescent organometalliciridium complex different from that in the light-emitting element 1 wasused for a light-emitting layer. Chemical formulae of materials used inthis example are shown below.

(Fabrication of Light-Emitting Element 1 and Comparative Light-EmittingElement 1)

First, indium tin oxide containing silicon oxide (ITSO) was depositedover a glass substrate 1100 by a sputtering method, so that a firstelectrode 1101 which serves as an anode was formed. The thickness was110 nm and the electrode area was 2 mm×2 mm.

Next, as pretreatment for forming the light-emitting element over thesubstrate 1100, the surface of the substrate was washed, baked at 200°C. for 1 hour, and subjected to UV ozone treatment for 370 seconds.

After that, the substrate 1100 was transferred into a vacuum evaporationapparatus where the pressure was reduced to approximately 10⁻⁴ Pa, andsubjected to vacuum baking at 170° C. for 30 minutes in a heatingchamber of the vacuum evaporation apparatus, and then the substrate 1100was cooled down for about 30 minutes.

Next, the substrate 1100 was fixed to a holder provided in the vacuumevaporation apparatus so that a surface of the substrate 1100 over whichthe first electrode 1101 was formed faced downward. In this example, acase will be described in which a hole-injection layer 1111, ahole-transport layer 1112, a light-emitting layer 1113, anelectron-transport layer 1114, and an electron-injection layer 1115which are included in an EL layer 1102 are sequentially formed.

After reducing the pressure of the vacuum evaporation apparatus to 10⁻⁴Pa, 1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II) andmolybdenum(VI) oxide were co-evaporated with a mass ratio of 4:2(=DBT3P-II (abbreviation):molybdenum oxide), so that the hole-injectionlayer 1111 was formed over the first electrode 1101. The thickness ofthe hole-injection layer 1111 was 40 nm. Note that a co-evaporationmethod is an evaporation method in which a plurality of differentsubstances is concurrently vaporized from respective differentevaporation sources.

Next, 9-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]-9H-carbazole (abbreviation:mCzFLP) was evaporated to a thickness of 20 nm, so that thehole-transport layer 1112 was formed.

Next, the light-emitting layer 1113 was formed over the hole-transportlayer 1112. In the case of the light-emitting element 1, thelight-emitting layer 1113 was formed by co-evaporation of4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), 9-phenyl-9H-3-(9-phenyl-9H-carbazol-3-yl)carbazole(abbreviation: PCCP), andbis[2-methyl-3-(6-tert-butyl-4-pyrimidinyl-κN3)pyridyl-κC](2,4-pentanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(tBumpypm)₂(acac)]) with a mass ratio of 0.8:0.2:0.025(=4,6mDBTP2 Pm-II (abbreviation):PCCP(abbreviation):[Ir(tBumpypm)₂(acac)] (abbreviation)) to a thickness of40 nm. In the case of the comparative light-emitting element 1, usingtris(2-phenylpyridinato)iridium(III) (abbreviation: [Ir(ppy)₃]) insteadof [Ir(tBumpypm)₂(acac)] (abbreviation), the light-emitting layer 1113was formed by co-evaporation of 4,6mDBTP2 Pm-II (abbreviation), PCCP(abbreviation), and [Ir(ppy)₃] (abbreviation) with a mass ratio of0.8:0.2:0.05 (=4,6mDBTP2 Pm-II (abbreviation):PCCP(abbreviation):[Ir(ppy)₃] (abbreviation)) to a thickness of 40 nm.

Then, 4,6mDBTP2Pm-II (abbreviation) was evaporated to a thickness of 10nm over the light-emitting layer 1113 and bathophenanthroline(abbreviation: Bphen) was evaporated to a thickness of 20 nm, so thatthe electron-transport layer 1114 was formed. Furthermore, lithiumfluoride was evaporated to a thickness of 1 nm over theelectron-transport layer 1114, so that the electron-injection layer 1115was formed.

Finally, aluminum was evaporated to a thickness of 200 nm over theelectron-injection layer 1115 to form a second electrode 1103 serving asa cathode; thus, the light-emitting element 1 and the comparativelight-emitting element 1 were obtained. Note that, in the aboveevaporation process, evaporation was all performed by a resistanceheating method.

Element structures of the light-emitting element 1 and the comparativelight-emitting element 1 obtained as described above are shown in Table1.

TABLE 1 Hole- Hole- Light- Electron- First injection transport emittingElectron-transport injection Second Electrode Layer Layer Layer LayerLayer Electrode Light-emitting ITSO * mCzFLP ** 4,6mDBTP2Pm- Bphen LiFAl Element 1 (110 nm) (20 nm) II (20 nm) (1 nm) (200 nm) (10 nm)Comparative ITSO * mCzFLP *** 4,6mDBTP2Pm- Bphen LiF Al Light emitting(110 nm) (20 nm) II (20 nm) (1 nm) (200 nm) Element 1 (10 nm) *DBT3P-II:MoOx (4:2, 40 nm) ** 4,6mDBTP2Pm-II:PCCP:[Ir(tBumpypm)₂(acac)](0.8:0.2:0.025, 40 nm) *** 4,6mDBTP2Pm-II:PCCP:[Ir(ppy)₃] (0.8:0.2:0.05,40 nm)

Further, after fabrication, each of the light-emitting element 1 and thecomparative light-emitting element 1 was sealed in a glove boxcontaining a nitrogen atmosphere so as not to be exposed to the air(specifically, a sealant was applied onto an outer edge of the elementand heat treatment was performed at 80° C. for 1 hour at the time ofsealing).

(Operation Characteristics of Light-Emitting Element 1 and ComparativeLight-Emitting Element 1)

Operation characteristics of the fabricated light-emitting element 1 andcomparative light-emitting element 1 were measured. Note that themeasurement was carried out at room temperature (in an atmosphere keptat 25° C.).

FIG. 16 shows voltage-luminance characteristics of the light-emittingelement 1 and the comparative light-emitting element 1. In FIG. 16, thevertical axis represents luminance (cd/m²) and the horizontal axisrepresents voltage (V). Further, FIG. 17 shows luminance-currentefficiency characteristics of the light-emitting element 1 and thecomparative light-emitting element 1. In FIG. 17, the vertical axisrepresents current efficiency (cd/A) and the horizontal axis representsluminance (cd/m²). Further, FIG. 18 shows luminance-external quantumefficiency characteristics of the light-emitting element 1 and thecomparative light-emitting element 1. In FIG. 18, the vertical axisrepresents external quantum efficiency (%) and the horizontal axisrepresents luminance (cd/m²).

From FIG. 18, it is found that the light-emitting element 1 in which thephosphorescent organometallic iridium complex [Ir(tBumpypm)₂(acac)](abbreviation) according to one embodiment of the present invention wasused in part of the light-emitting layer has higher efficiency than thecomparative light-emitting element 1 in which [Ir(ppy)₃] (abbreviation)was used in part of the light-emitting layer. In addition, Table 2 belowshows initial values of main characteristics of the light-emittingelement 1 and the comparative light-emitting element 1 at a luminance ofabout 900 cd/m².

TABLE 2 External Current Current Power Quantum Voltge Current DensityChromaticity Luminance Efficiency Efficiency Efficiency (V) (mA)(mA/cm²) (x, y) (cd/m²) (cd/A) (lm/W) (%) Light-emitting 3.3 0.045 1.1(0.29, 0.60) 900 80 76 25 Element 1 Comparative 3.5 0.053 1.3 (0.34,0.60) 870 66 59 19 Light-emitting Element 1

From the above results, it is found that the light-emitting element 1fabricated in this example has higher external quantum efficiency(higher emission efficiency) than the comparative light-emitting element1. Note that from the chromaticity, it is found that the light-emittingelement 1 emits green light.

FIG. 19 shows emission spectra of the light-emitting element 1 and thecomparative light-emitting element 1 when a current at a current densityof 0.1 mA/cm² was supplied thereto. As shown in FIG. 19, the emissionspectrum of the light-emitting element 1 has a peak around 510 nm and itis indicated that the peak is derived from emission of thephosphorescent organometallic iridium complex [Ir(tBumpypm)₂(acac)](abbreviation). On the other hand, the emission spectrum of thecomparative light-emitting element 1 has a peak around 516 nm and it issuggested that the peak is derived from emission of the phosphorescentorganometallic iridium complex [Ir(ppy)₃] (abbreviation).

Example 5

In this example, a light-emitting element 2 in which the phosphorescentorganometallic iridium complextris[2-methyl-3-(6-tert-butyl-4-pyrimidinyl-κN3)pyridyl-κC]iridium(III)(abbreviation: [Ir(tBumpypm)₃]) (the structural formula (102)) was usedfor a light-emitting layer will be described. Further, a comparativelight-emitting element 2 in which a phosphorescent organometalliciridium complex different from that in the light-emitting element 2 wasused for a light-emitting layer will be described. Note that in thedescription of the light-emitting element 2 and the comparativelight-emitting element 2 in this example, FIG. 15 which is used in thedescription of the light-emitting element 1 and the comparativelight-emitting element 1 in Example 4 is to be referred to. Chemicalformulae of materials used in this example are shown below.

(Fabrication of Light-Emitting Element 2 and Comparative Light-EmittingElement 2)

First, indium tin oxide containing silicon oxide (ITSO) was depositedover the glass substrate 1100 by a sputtering method, so that the firstelectrode 1101 which serves as an anode was formed. The thickness was110 nm and the electrode area was 2 mm×2 mm.

Next, as pretreatment for forming the light-emitting element over thesubstrate 1100, the surface of the substrate was washed, baked at 200°C. for 1 hour, and subjected to UV ozone treatment for 370 seconds.

After that, the substrate 1100 was transferred into a vacuum evaporationapparatus where the pressure was reduced to approximately 10⁻⁴ Pa, andsubjected to vacuum baking at 170° C. for 30 minutes in a heatingchamber of the vacuum evaporation apparatus, and then the substrate 1100was cooled down for about 30 minutes.

Next, the substrate 1100 was fixed to a holder provided in the vacuumevaporation apparatus so that a surface of the substrate 1100 over whichthe first electrode 1101 was formed faced downward. In this example, acase will be described in which the hole-injection layer 1111, thehole-transport layer 1112, the light-emitting layer 1113, theelectron-transport layer 1114, and the electron-injection layer 1115which are included in the EL layer 1102 are sequentially formed.

After reducing the pressure of the vacuum evaporation apparatus to 10⁻⁴Pa, 1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II) andmolybdenum(VI) oxide were co-evaporated with a mass ratio of 4:2(=DBT3P-II (abbreviation):molybdenum oxide), so that the hole-injectionlayer 1111 was formed over the first electrode 1101. The thickness ofthe hole-injection layer 1111 was 40 nm Note that a co-evaporationmethod is an evaporation method in which a plurality of differentsubstances is concurrently vaporized from respective differentevaporation sources.

Next, 9-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]-9H-carbazole (abbreviation:mCzFLP) was evaporated to a thickness of 20 nm, so that thehole-transport layer 1112 was formed.

Next, the light-emitting layer 1113 was formed over the hole-transportlayer 1112. In the case of the light-emitting element 2, thelight-emitting layer 1113 having a stacked structure was formed in thefollowing manner. First, 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine(abbreviation: 4,6mCzP2 Pm),9-phenyl-9H-3-(9-phenyl-9H-carbazol-3-yl)carbazole (abbreviation: PCCP),andtris[2-methyl-3-(6-tert-butyl-4-pyrimidinyl-κN3)pyridyl-κC]iridium(III)(abbreviation: [Ir(tBumpypm)₃]) were co-evaporated with a mass ratio of0.5:0.5:0.05 (=4,6mCzP2Pm (abbreviation):PCCP(abbreviation):[Ir(tBumpypm)₃] (abbreviation)) to a thickness of nm, andthen 4,6mCzP2 Pm (abbreviation), PCCP (abbreviation), and[Ir(tBumpypm)₃] (abbreviation) were co-evaporated with a mass ratio of0.8:0.2:0.05 (=4,6mCzP2 Pm (abbreviation):PCCP(abbreviation):[Ir(tBumpypm)₃] (abbreviation)) to a thickness of 20 nm.In the case of the comparative light-emitting element 2, usingtris(2-phenylpyridinato)iridium(III) (abbreviation: [Ir(ppy)₃]) insteadof [Ir(tBumpypm)₃] (abbreviation), the light-emitting layer 1113 wasformed by co-evaporation of 4,6mCzP2 Pm (abbreviation), PCCP(abbreviation), and [Ir(ppy)₃] (abbreviation) with a mass ratio of0.8:0.2:0.05 (=4,6mCzP2 Pm (abbreviation):PCCP (abbreviation):[Ir(ppy)₃] (abbreviation)) to a thickness of 40 nm.

Then, 4,6mCzP2 Pm (abbreviation) was evaporated to a thickness of 10 nmover the light-emitting layer 1113 and bathophenanthroline(abbreviation: Bphen) was evaporated to a thickness of 20 nm, so thatthe electron-transport layer 1114 was formed. Furthermore, lithiumfluoride was evaporated to a thickness of 1 nm over theelectron-transport layer 1114, so that the electron-injection layer 1115was formed.

Finally, aluminum was evaporated to a thickness of 200 nm over theelectron-injection layer 1115 to form the second electrode 1103 servingas a cathode; thus, the light-emitting element 2 and the comparativelight-emitting element 2 were obtained. Note that, in the aboveevaporation process, evaporation was all performed by a resistanceheating method.

Element structures of the light-emitting element 2 and the comparativelight-emitting element 2 obtained as described above are shown in Table3.

TABLE 3 Hole- Hole- Light- Electron- First injection transport emittingElectron-transport injection Second Electrode Layer Layer Layer LayerLayer Electrode Light-emitting ITSO * mCzFLP ** 4,6mCzP2Pm Bphen LiF AlElement 2 (110 nm) (20 nm) (10 nm) (20 nm) (1 nm) (200 nm) ComparativeITSO * mCzFLP *** 4,6mCzP2Pm Bphen LiF Al Light-emitting (110 nm) (20nm) (10 nm) (20 nm) (1 nm) (200 nm) Element 2 * DBT3P-II: MoOx (4:2, 40nm) ** 4,6mCzP2Pm:PCCP:[Ir(tBumpypm)₃] (0.5:0.5:0.05 20 nm\0.8:0.2:0.05,20 nm) *** 4,6mCzP2Pm:PCCP:[Ir(ppy)₃] (0.8:0.2:0.05, 40 nm)

Further, after fabrication, each of the light-emitting element 2 and thecomparative light-emitting element 2 was sealed in a glove boxcontaining a nitrogen atmosphere so as not to be exposed to the air(specifically, a sealant was applied onto an outer edge of the elementand heat treatment was performed at 80° C. for 1 hour at the time ofsealing).

(Operation Characteristics of Light-Emitting Element 2 and ComparativeLight-Emitting Element 2)

Operation characteristics of the fabricated light-emitting element 2 andcomparative light-emitting element 2 were measured. Note that themeasurement was carried out at room temperature (in an atmosphere keptat 25° C.).

FIG. 20 shows voltage-luminance characteristics of the light-emittingelement 2 and the comparative light-emitting element 2. In FIG. 20, thevertical axis represents luminance (cd/m²) and the horizontal axisrepresents voltage (V). Further, FIG. 21 shows luminance-currentefficiency characteristics of the light-emitting element 2 and thecomparative light-emitting element 2. In FIG. 21, the vertical axisrepresents current efficiency (cd/A) and the horizontal axis representsluminance (cd/m²). Further, FIG. 22 shows luminance-external quantumefficiency characteristics of the light-emitting element 2 and thecomparative light-emitting element 2. In FIG. 22, the vertical axisrepresents external quantum efficiency (%) and the horizontal axisrepresents luminance (cd/m²).

From FIG. 22, it is found that the light-emitting element 2 in which thephosphorescent organometallic iridium complex [Ir(tBumpypm)₃](abbreviation) according to one embodiment of the present invention wasused in part of the light-emitting layer has higher efficiency than thecomparative light-emitting element 2 in which [Ir(ppy)₃] (abbreviation)was used in part of the light-emitting layer. In addition, Table 4 belowshows initial values of main characteristics of the light-emittingelement 2 and the comparative light-emitting element 2 at a luminance ofabout 1000 cd/m².

TABLE 4 External Current Current Power Quantum Voltge Current DensityChromaticity Luminance Efficiency Efficiency Efficiency (V) (mA)(mA/cm²) (x, y) (cd/m²) (cd/A) (lm/W) (%) Light-emitting 3.4 0.067 1.7(0.24, 0.50) 960 57 53 21 Element 2 Comparative 3.7 0.068 1.7 (0.34,0.61) 1100 65 55 19 Light-emitting Element 2

From the above results, it is found that the light-emitting element 2fabricated in this example has higher external quantum efficiency(higher emission efficiency) than the comparative light-emitting element2. Note that from the chromaticity, it is found that the light-emittingelement 2 emits blue green light whereas the comparative light-emittingelement 2 emits green light.

FIG. 23 shows emission spectra of the light-emitting element 2 and thecomparative light-emitting element 2 when a current at a current densityof 0.1 mA/cm² was supplied thereto. As shown in FIG. 23, the emissionspectrum of the light-emitting element 2 has a peak around 490 nm and itis indicated that the peak is derived from emission of thephosphorescent organometallic iridium complex [Ir(tBumpypm)₃](abbreviation). On the other hand, the emission spectrum of thecomparative light-emitting element 2 has a peak around 514 nm and it issuggested that the peak is derived from emission of the phosphorescentorganometallic iridium complex [Ir(ppy)₃] (abbreviation).

Reference Synthetic Example

A method for synthesizing9-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]-9H-carbazole (abbreviation:mCzFLP) used in part of the light-emitting elements fabricated inExamples 4 and 5 will be described.

Synthetic Method of 9-[3-(9-Phenyl-9H-fluoren-9-yl)phenyl]-9H-carbazole(abbreviation: mCzFLP)

A structure of mCzFLP (abbreviation) is shown below.

In a 100 mL three-neck flask, 4.9 g (12.4 mmol) of9-(3-bromophenyl)-9-phenylfluorene, 2.1 g (12.4 mmol) of carbazole, and3.6 g (37.2 mmol) of sodium tert-butoxide were put, and the air in theflask was replaced with nitrogen. To this mixture, 31.0 mL of xylene,0.2 mL of a 10% hexane solution of tri(tert-butyl)phosphine, and 48.1 mg(0.1 mmol) of bis(dibenzylideneacetone)palladium(0) were added, and theobtained mixture was stirred at 140° C. for 3.5 hours. After thestirring, 47.7 mg (0.1 mmol) of bis(dibenzylideneacetone)palladium(0)and 0.6 mL of a 10% hexane solution of tri(tert-butyl)phosphine wereadded, and the obtained mixture was stirred for 1.5 hours.

After the stirring, 70 mL of ethyl acetate and 150 mL of toluene wereadded, heating was performed, and suction filtration through Florisil,Celite, and alumina was performed to give a filtrate. The resultingfiltrate was condensed to give a solid. The resulting solid was purifiedby silica gel column chromatography (a developing solvent: hexane andtoluene in a 7:3 ratio) to give a target white solid. The resultingwhite solid was recrystallized from a mixed solvent of toluene andhexane to give 2.7 g of a target white solid in a yield of 46%.

Then, 1.5 g of the resulting white solid was purified by a trainsublimation method. In the purification by sublimation, the white solidwas heated at 186° C. under a pressure of 2.7 Pa with an argon flow rateof 5.0 mL/min. After the purification by sublimation, 1.4 g of a whitesolid which was a target substance was obtained at a collection rate of93%. The reaction scheme of the synthetic method is shown in (D-1)below.

The compound obtained by the above synthetic scheme (D-1) was measuredby a nuclear magnetic resonance method (¹H NMR). The measurement dataare shown below.

¹H NMR (CDCl₃, 500 MHz): δ=7.19-7.49 (m, 21H), 7.77 (d, J=7.5 Hz, 2H),8.10 (d, J=7.0 Hz, 2H).

Example 6 Synthetic Example 4

This example shows a method for synthesizing the phosphorescentorganometallic iridium complexbis{2-methyl-3-[6-(2,5-dimethylphenyl)-4-pyrimidinyl-κN3]pyridyl-κC4}(2,4-pentanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmpmpypm)₂(acac)]) represented by the structuralformula (117) in Embodiment 1 according to one embodiment of the presentinvention. A structure of [Ir(dmpmpypm)₂(acac)] (abbreviation) is shownbelow.

Step 1: Synthesis of 4-Chloro-6-(2,5-dimethylphenyl)pyrimidine

First, 4.97 g of 4,6-dichloropyrimidine, 5.02 g of2,5-dimethylphenylboronic acid, 3.55 g of sodium carbonate, 0.29 g ofbis(triphenylphosphine)palladium(II)dichloride (abbreviation:Pd(PPh₃)₂Cl₂), 20 mL of water, and 20 mL of acetonitrile were put in arecovery flask equipped with a reflux pipe, and the air in the flask wasreplaced with argon. This reaction container was heated by beingirradiated with microwaves (2.45 GHz, 100 W) for 30 minutes. Further,1.25 g of 2,5-dimethylphenylboronic acid, 0.89 g of sodium carbonate,and 0.073 g of Pd(PPh₃)₂Cl₂ were put in the flask, and the reactioncontainer was heated again by being irradiated with microwaves (2.45GHz, 100 W) for 30 minutes. Then, water was added to this solution andan organic layer was extracted with dichloromethane. The obtainedorganic layer was washed with water and saturated brine, and was driedwith magnesium sulfate. After the drying, the solution was filtered. Thesolvent of this solution was distilled off, and then the obtainedresidue was purified by flash column chromatography using hexane andethyl acetate in a ratio of 5:1 as a developing solvent, so that thetarget pyrimidine derivative was obtained (pale yellow oily substance,yield of 64%). A synthetic scheme of Step 1 is shown in (d-1) below.

Step 2: Synthesis of4-(2,5-Dimethylphenyl)-6-(2-methylpyridin-3-yl)pyrimidine (abbreviation:Hdmpmpypm)

Next, 1.98 g of 4-chloro-6-(2,5-dimethylphenyl)pyrimidine obtained inthe above Step 1, 2.41 g of 2-methylpyridine-3-boronic acid pinacolester, 14 mL of 1M aqueous solution of potassium acetate, 14 mL of 1Maqueous solution of sodium carbonate, and 30 mL of acetonitrile were putin a 100 mL round-bottom flask, and the air in the flask was replacedwith argon. Then, 0.63 g of tetrakis(triphenylphosphine)palladium(0) wasadded to this mixture, and the reaction container was heated by beingirradiated with microwaves (2.45 GHz, 100 W) for 60 minutes. Thisreaction mixture was extracted with ethyl acetate, and washing withsaturated brine was performed. Anhydrous magnesium sulfate was added tothe obtained solution of the extract for drying, and the resultingmixture was gravity-filtered to give a filtrate. The residue obtained bycondensing the filtrate was purified by flash column chromatographyusing hexane and ethyl acetate in a ratio of 1:1 as a developingsolvent. The fraction was condensed and the obtained oily substance wasdissolved in dichloromethane. Then, filtration was performed through afilter aid in which Celite, alumina, and Celite were stacked in thisorder, so that the target pyrimidine derivative Hdmpmpypm (abbreviation)was obtained (orange oily substance, a yield of 87%). A synthetic schemeof Step 2 is shown in (d-2) below.

(Step 3: Synthesis ofDi-μ-chloro-tetrakis{2-methyl-3-[6-(2,5-dimethylphenyl)-4-pyrimidinyl-κN3]pyridyl-κC4}diiridium(III)(abbreviation: [Ir(dmpmpypm)₂Cl]₂)

Next, 15 mL of 2-ethoxyethanol, 5 mL of water, 2.23 g of the ligandHdmpmpypm obtained in the above Step 2, and 1.13 g of iridium chloridehydrate (IrCl₃.H₂O) (produced by Sigma-Aldrich Corp.) were put in arecovery flask equipped with a reflux pipe, and the air in the flask wasreplaced with argon. Then, microwave irradiation (2.45 GHz, 100 W) wasperformed for 1 hour to cause a reaction. The solvent was distilled off,and then the obtained residue was suction-filtered and washed, so thatthe target dinuclear complex [Ir(dmpmpypm)₂Cl]₂ (abbreviation) wasobtained (reddish brown solid, yield of 80%). A synthetic scheme of Step3 is shown in (d-3) below.

Step 4: Synthesis ofBis{2-methyl-3-[6-(2,5-dimethylphenyl)-4-pyrimidinyl-κN3]pyridyl-κC4}(2,4-pentanedionato-κ²O,O′)iridium(III) (abbreviation: [Ir(dmpmpypm)₂(acac)])

Next, 2.24 g of the dinuclear complex [Ir(dmpmpypm)₂Cl]₂ obtained in theabove Step 3, 1.50 g of sodium carbonate, 0.42 g of acetylacetone, and40 mL of 2-ethoxyethanol were put in a 100 mL round-bottom flask, andthe air in the flask was replaced with argon. Then, heating wasperformed by irradiation with microwaves (2.45 GHz, 100 W) for 1 hour.Further, 0.42 g of acetylacetone was put in the flask, and heating wasagain performed by irradiation with microwaves (2.45 GHz, 100 W) for 1hour. The solvent was distilled off, the obtained residue was dissolvedin dichloromethane, and washing was performed with water and saturatedbrine. The obtained organic layer was dried with magnesium sulfate.After the drying, the solution was filtered. The solvent of thissolution was distilled off, and the obtained residue was purified byflash column chromatography using ethyl acetate and methanol in a ratioof 4:1 as a developing solvent. The fraction was condensed, and theobtained solid was purified by flash column chromatography using ethylacetate as a developing solvent. Then, recrystallization was performedwith a mixed solvent of ethyl acetate and hexane, so that thephosphorescent organometallic iridium complex [Ir(dmpmpypm)₂(acac)](abbreviation) according to one embodiment of the present invention wasobtained (yellow orange powder, yield of 8%). A synthetic scheme of Step4 is shown in (d-4) below.

Results of analysis of the yellow orange powder obtained in the aboveStep 4 by nuclear magnetic resonance spectrometry (¹H-NMR) are shownbelow. The ¹H-NMR chart is shown in FIG. 27. These results revealed thatthe phosphorescent organometallic iridium complex [Ir(dmpmpypm)₂(acac)](abbreviation) represented by the structural formula (117) according toone embodiment of the present invention was obtained in SyntheticExample 4.

¹H-NMR. δ (DMSO-d6): 1.82 (s, 6H), 2.40 (s, 6H), 2.56 (s, 6H), 2.91 (s,6H), 5.43 (s, 1H), 6.20 (d, 2H), 7.30 (d, 2H), 7.35 (d, 2H), 7.51 (d,2H), 7.69 (s, 2H), 8.32 (s, 2H), 9.11 (s, 2H).

Next, an ultraviolet-visible absorption spectrum (hereinafter, simplyreferred to as an “absorption spectrum”) of a dichloromethane solutionof [Ir(dmpmpypm)₂(acac)] (abbreviation) and an emission spectrum thereofwere measured. The absorption spectrum was measured with anultraviolet-visible spectrophotometer (V-550, produced by JASCOCorporation) using a dichloromethane solution (0.083 mmol/L) put in aquartz cell at room temperature. Further, the emission spectrum wasmeasured with a fluorescence spectrophotometer (FS920, produced byHamamatsu Photonics K.K.) using a degassed dichloromethane solution(0.083 mmol/L) put in a quartz cell at room temperature. FIG. 28 showsmeasurement results of the absorption spectrum and emission spectrum. InFIG. 28, the horizontal axis represents wavelength and the vertical axesrepresent absorption intensity and emission intensity. In FIG. 28, twosolid lines are shown; a thin line represents the absorption spectrum,and a thick line represents the emission spectrum. The absorptionspectrum in FIG. 28 is the results obtained in such a way that theabsorption spectrum measured by putting only dichloromethane in a quartzcell was subtracted from the absorption spectrum measured by putting thedichloromethane solution (0.083 mmol/L) in a quartz cell.

As shown in FIG. 28, the phosphorescent organometallic iridium complex[ft(dmpmpypm)₂(acac)] (abbreviation) according to one embodiment of thepresent invention has an emission peak at 535 nm, and yellow green lightemission was observed from the dichloromethane solution.

This application is based on Japanese Patent Application serial no.2012-096275 filed with Japan Patent Office on Apr. 20, 2012 and JapanesePatent Application serial no. 2013-049025 filed with Japan Patent Officeon Mar. 12, 2013, the entire contents of which are hereby incorporatedby reference.

What is claimed is:
 1. A light-emitting element comprising a compoundrepresented by a formula (G2)

wherein: R¹ and R⁴ to R⁶ separately represent hydrogen or an alkyl grouphaving 1 to 6 carbon atoms, R² and R³ separately represent any ofhydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted orunsubstituted phenyl group, and a substituted or unsubstituted pyridylgroup, and L represents a monoanionic ligand.
 2. A light-emitting devicecomprising the light-emitting element according to claim
 1. 3. Anelectronic device comprising the light-emitting device according toclaim
 2. 4. A lighting device comprising the light-emitting deviceaccording to claim
 2. 5. The light-emitting element according to claim1, wherein: the monoanionic ligand is represented by one of formulae(L1) to (L6)

R¹¹ to R⁴² separately represent any of hydrogen, a substituted orunsubstituted alkyl group having 1 to 4 carbon atoms, halogen, a vinylgroup, a substituted or unsubstituted haloalkyl group having 1 to 4carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 4carbon atoms, and a substituted or unsubstituted alkylthio group having1 to 4 carbon atoms, and A¹ to A³ separately represent any of nitrogen,sp2 hybridized carbon bonded to hydrogen, and sp2 hybridized carbonbonded to any of an alkyl group having 1 to 4 carbon atoms, halogen, ahaloalkyl group having 1 to 4 carbon atoms, and a phenyl group.
 6. Thelight-emitting element according to claim 1, wherein the compound isrepresented by a formula (100)


7. The light-emitting element according to claim 1, wherein the compoundis represented by a formula (101)


8. The light-emitting element according to claim 1, wherein the compoundis represented by a formula (117)